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	$228.74	4.206%	$238.3608	$238.36	$238.35	$238.40
Purchase #2	$194.33	7.277%	$208.4714	$208.47	$208.45	$208.50
Purchase #3	$85.25	12.748%	$96.1177	$96.12	$96.10	$96.10
Purchase #4	$224.90	10.510%	$248.537	$248.54	$248.55	$248.50
Purchase #5	$68.73	6.718%	$73.3473	$73.35	$73.35	$73.30
Purchase #6	$30.37	4.357%	$31.6932	$31.69	$31.70	$31.70
Purchase #7	$95.46	10.678%	$105.6532	$105.65	$105.65	$105.70
7 purchase totals =	$927.78		$1,002.1806	$1,002.18	$1,002.15	$1,002.20