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	$185.35	7.499%	$199.2494	$199.25	$199.25	$199.20
Purchase #2	$125.36	9.500%	$137.2692	$137.27	$137.25	$137.30
Purchase #3	$58.65	4.449%	$61.2593	$61.26	$61.25	$61.30
Purchase #4	$166.55	3.799%	$172.8772	$172.88	$172.90	$172.90
Purchase #5	$50.63	10.570%	$55.9816	$55.98	$56.00	$56.00
Purchase #6	$43.29	3.288%	$44.7134	$44.71	$44.70	$44.70
Purchase #7	$19.94	3.249%	$20.5879	$20.59	$20.60	$20.60
7 purchase totals =	$649.77		$691.9380	$691.94	$691.95	$692.00