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	$131.59	8.183%	$142.358	$142.36	$142.35	$142.40
Purchase #2	$134.72	12.552%	$151.6301	$151.63	$151.65	$151.60
Purchase #3	$167.27	3.363%	$172.8953	$172.90	$172.90	$172.90
Purchase #4	$49.95	4.550%	$52.2227	$52.22	$52.20	$52.20
Purchase #5	$38.91	9.337%	$42.543	$42.54	$42.55	$42.50
Purchase #6	$66.30	3.578%	$68.6722	$68.67	$68.65	$68.70
Purchase #7	$48.94	13.727%	$55.658	$55.66	$55.65	$55.70
7 purchase totals =	$637.68		$685.9793	$685.98	$685.95	$686.00