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	$78.88	13.405%	$89.4539	$89.45	$89.45	$89.50
Purchase #2	$166.69	4.262%	$173.7943	$173.79	$173.80	$173.80
Purchase #3	$205.55	13.319%	$232.9272	$232.93	$232.95	$232.90
Purchase #4	$189.98	4.770%	$199.042	$199.04	$199.05	$199.00
Purchase #5	$116.91	13.273%	$132.4275	$132.43	$132.45	$132.40
Purchase #6	$20.77	9.561%	$22.7558	$22.76	$22.75	$22.80
Purchase #7	$156.74	6.289%	$166.5974	$166.60	$166.60	$166.60
7 purchase totals =	$935.52		$1,016.9981	$1,017.00	$1,017.05	$1,017.00