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	$155.55	10.320%	$171.6028	$171.60	$171.60	$171.60
Purchase #2	$105.61	10.223%	$116.4065	$116.41	$116.40	$116.40
Purchase #3	$5.30	3.526%	$5.4869	$5.49	$5.50	$5.50
Purchase #4	$55.54	5.663%	$58.6852	$58.69	$58.70	$58.70
Purchase #5	$83.88	13.510%	$95.2122	$95.21	$95.20	$95.20
Purchase #6	$62.48	9.429%	$68.3712	$68.37	$68.35	$68.40
Purchase #7	$113.37	12.810%	$127.8927	$127.89	$127.90	$127.90
7 purchase totals =	$581.73		$643.6575	$643.66	$643.65	$643.70