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	$117.51	13.420%	$133.2798	$133.28	$133.30	$133.30
Purchase #2	$85.58	4.269%	$89.2334	$89.23	$89.25	$89.20
Purchase #3	$166.56	13.728%	$189.4254	$189.43	$189.45	$189.40
Purchase #4	$176.70	9.731%	$193.8947	$193.89	$193.90	$193.90
Purchase #5	$81.81	12.665%	$92.1712	$92.17	$92.15	$92.20
Purchase #6	$72.54	6.499%	$77.2544	$77.25	$77.25	$77.30
Purchase #7	$225.77	9.273%	$246.7057	$246.71	$246.70	$246.70
7 purchase totals =	$926.47		$1,021.9646	$1,021.96	$1,022.00	$1,022.00