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	$46.30	12.216%	$51.956	$51.96	$51.95	$52.00
Purchase #2	$16.83	10.118%	$18.5329	$18.53	$18.55	$18.50
Purchase #3	$35.71	6.747%	$38.1194	$38.12	$38.10	$38.10
Purchase #4	$151.33	10.170%	$166.7203	$166.72	$166.70	$166.70
Purchase #5	$99.83	8.653%	$108.4683	$108.47	$108.45	$108.50
Purchase #6	$224.69	10.456%	$248.1836	$248.18	$248.20	$248.20
Purchase #7	$92.69	10.371%	$102.3029	$102.30	$102.30	$102.30
7 purchase totals =	$667.38		$734.2834	$734.28	$734.25	$734.30