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	$106.28	5.154%	$111.7577	$111.76	$111.75	$111.80
Purchase #2	$135.67	4.534%	$141.8213	$141.82	$141.80	$141.80
Purchase #3	$215.77	6.151%	$229.042	$229.04	$229.05	$229.00
Purchase #4	$210.50	6.530%	$224.2457	$224.25	$224.25	$224.20
Purchase #5	$165.31	11.849%	$184.8976	$184.90	$184.90	$184.90
Purchase #6	$121.72	6.475%	$129.6014	$129.60	$129.60	$129.60
Purchase #7	$35.29	13.236%	$39.961	$39.96	$39.95	$40.00
7 purchase totals =	$990.54		$1,061.3267	$1,061.33	$1,061.30	$1,061.30