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	$109.95	4.747%	$115.1693	$115.17	$115.15	$115.20
Purchase #2	$108.96	10.729%	$120.6503	$120.65	$120.65	$120.70
Purchase #3	$54.30	9.614%	$59.5204	$59.52	$59.50	$59.50
Purchase #4	$243.79	6.624%	$259.9386	$259.94	$259.95	$259.90
Purchase #5	$88.27	6.302%	$93.8328	$93.83	$93.85	$93.80
Purchase #6	$107.91	3.467%	$111.6512	$111.65	$111.65	$111.70
Purchase #7	$153.50	13.762%	$174.6247	$174.62	$174.60	$174.60
7 purchase totals =	$866.68		$935.3873	$935.38	$935.35	$935.40