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	$33.49	9.728%	$36.7479	$36.75	$36.75	$36.70
Purchase #2	$89.87	11.850%	$100.5196	$100.52	$100.50	$100.50
Purchase #3	$139.52	13.319%	$158.1027	$158.10	$158.10	$158.10
Purchase #4	$238.67	6.260%	$253.6107	$253.61	$253.60	$253.60
Purchase #5	$86.54	4.281%	$90.2448	$90.24	$90.25	$90.20
Purchase #6	$242.97	9.753%	$266.6669	$266.67	$266.65	$266.70
Purchase #7	$63.65	6.373%	$67.7064	$67.71	$67.70	$67.70
7 purchase totals =	$894.71		$973.5990	$973.60	$973.55	$973.50