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	$151.31	9.285%	$165.3591	$165.36	$165.35	$165.40
Purchase #2	$83.28	12.721%	$93.874	$93.87	$93.85	$93.90
Purchase #3	$87.37	10.518%	$96.5596	$96.56	$96.55	$96.60
Purchase #4	$197.47	9.110%	$215.4595	$215.46	$215.45	$215.50
Purchase #5	$104.49	5.223%	$109.9475	$109.95	$109.95	$109.90
Purchase #6	$32.71	9.519%	$35.8237	$35.82	$35.80	$35.80
Purchase #7	$40.93	3.616%	$42.41	$42.41	$42.40	$42.40
7 purchase totals =	$697.56		$759.4334	$759.43	$759.35	$759.50