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	$241.34	9.669%	$264.6752	$264.68	$264.70	$264.70
Purchase #2	$100.76	10.172%	$111.0093	$111.01	$111.00	$111.00
Purchase #3	$54.95	6.112%	$58.3085	$58.31	$58.30	$58.30
Purchase #4	$63.42	13.694%	$72.1047	$72.10	$72.10	$72.10
Purchase #5	$78.93	13.676%	$89.7245	$89.72	$89.70	$89.70
Purchase #6	$35.34	9.862%	$38.8252	$38.83	$38.85	$38.80
Purchase #7	$82.76	6.645%	$88.2594	$88.26	$88.25	$88.30
7 purchase totals =	$657.50		$722.9068	$722.91	$722.90	$722.90