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	$84.60	12.502%	$95.1767	$95.18	$95.20	$95.20
Purchase #2	$142.72	10.324%	$157.4544	$157.45	$157.45	$157.50
Purchase #3	$98.83	5.628%	$104.3922	$104.39	$104.40	$104.40
Purchase #4	$65.81	3.663%	$68.2206	$68.22	$68.20	$68.20
Purchase #5	$158.31	3.810%	$164.3416	$164.34	$164.35	$164.30
Purchase #6	$54.43	9.756%	$59.7402	$59.74	$59.75	$59.70
Purchase #7	$219.25	4.821%	$229.82	$229.82	$229.80	$229.80
7 purchase totals =	$823.95		$879.1457	$879.14	$879.15	$879.10