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	$42.46	7.399%	$45.6016	$45.60	$45.60	$45.60
Purchase #2	$56.61	7.676%	$60.9554	$60.96	$60.95	$61.00
Purchase #3	$78.41	5.824%	$82.9766	$82.98	$83.00	$83.00
Purchase #4	$20.50	5.483%	$21.624	$21.62	$21.60	$21.60
Purchase #5	$13.97	3.837%	$14.506	$14.51	$14.50	$14.50
Purchase #6	$188.72	10.355%	$208.262	$208.26	$208.25	$208.30
Purchase #7	$96.91	6.570%	$103.277	$103.28	$103.30	$103.30
7 purchase totals =	$497.58		$537.2026	$537.21	$537.20	$537.30