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	$107.96	8.542%	$117.1819	$117.18	$117.20	$117.20
Purchase #2	$169.76	9.267%	$185.4917	$185.49	$185.50	$185.50
Purchase #3	$115.37	11.866%	$129.0598	$129.06	$129.05	$129.10
Purchase #4	$84.48	12.644%	$95.1617	$95.16	$95.15	$95.20
Purchase #5	$228.77	11.258%	$254.5249	$254.52	$254.50	$254.50
Purchase #6	$152.91	6.447%	$162.7681	$162.77	$162.75	$162.80
Purchase #7	$74.57	5.555%	$78.7124	$78.71	$78.70	$78.70
7 purchase totals =	$933.82		$1,022.9005	$1,022.89	$1,022.85	$1,023.00