Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$172.43	12.667%	$194.2717	$194.27	$194.25	$194.30
Purchase #2	$181.93	3.585%	$188.4522	$188.45	$188.45	$188.50
Purchase #3	$124.52	3.210%	$128.5171	$128.52	$128.50	$128.50
Purchase #4	$183.25	13.234%	$207.5013	$207.50	$207.50	$207.50
Purchase #5	$209.70	13.867%	$238.7791	$238.78	$238.80	$238.80
Purchase #6	$131.29	10.850%	$145.535	$145.54	$145.55	$145.50
Purchase #7	$102.26	12.383%	$114.9229	$114.92	$114.90	$114.90
7 purchase totals =	$1,105.38		$1,217.9793	$1,217.98	$1,217.95	$1,218.00