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	$17.33	9.369%	$18.9536	$18.95	$18.95	$19.00
Purchase #2	$73.61	3.428%	$76.1334	$76.13	$76.15	$76.10
Purchase #3	$189.74	4.516%	$198.3087	$198.31	$198.30	$198.30
Purchase #4	$215.64	4.140%	$224.5675	$224.57	$224.55	$224.60
Purchase #5	$136.47	13.846%	$155.3656	$155.37	$155.35	$155.40
Purchase #6	$88.72	12.568%	$99.8703	$99.87	$99.85	$99.90
Purchase #7	$207.64	10.819%	$230.1046	$230.10	$230.10	$230.10
7 purchase totals =	$929.15		$1,003.3037	$1,003.30	$1,003.25	$1,003.40