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	$56.38	8.684%	$61.276	$61.28	$61.30	$61.30
Purchase #2	$230.48	4.668%	$241.2388	$241.24	$241.25	$241.20
Purchase #3	$111.64	6.229%	$118.5941	$118.59	$118.60	$118.60
Purchase #4	$92.81	11.632%	$103.6057	$103.61	$103.60	$103.60
Purchase #5	$156.87	9.836%	$172.2997	$172.30	$172.30	$172.30
Purchase #6	$170.31	13.430%	$193.1826	$193.18	$193.20	$193.20
Purchase #7	$94.46	8.332%	$102.3304	$102.33	$102.35	$102.30
7 purchase totals =	$912.95		$992.5273	$992.53	$992.60	$992.50