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	$78.61	13.680%	$89.3638	$89.36	$89.35	$89.40
Purchase #2	$195.34	6.631%	$208.293	$208.29	$208.30	$208.30
Purchase #3	$22.57	7.537%	$24.2711	$24.27	$24.25	$24.30
Purchase #4	$30.94	9.592%	$33.9078	$33.91	$33.90	$33.90
Purchase #5	$242.49	4.437%	$253.2493	$253.25	$253.25	$253.20
Purchase #6	$62.45	13.106%	$70.6347	$70.63	$70.65	$70.60
Purchase #7	$59.62	13.173%	$67.4737	$67.47	$67.45	$67.50
7 purchase totals =	$692.02		$747.1934	$747.18	$747.15	$747.20