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	$168.58	11.203%	$187.466	$187.47	$187.45	$187.50
Purchase #2	$36.29	3.196%	$37.4498	$37.45	$37.45	$37.40
Purchase #3	$130.90	4.836%	$137.2303	$137.23	$137.25	$137.20
Purchase #4	$40.78	10.650%	$45.1231	$45.12	$45.10	$45.10
Purchase #5	$191.59	6.855%	$204.7235	$204.72	$204.70	$204.70
Purchase #6	$223.34	9.350%	$244.2223	$244.22	$244.20	$244.20
Purchase #7	$72.47	11.543%	$80.8352	$80.84	$80.85	$80.80
7 purchase totals =	$863.95		$937.0502	$937.05	$937.00	$936.90