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	$54.98	12.330%	$61.759	$61.76	$61.75	$61.80
Purchase #2	$75.82	9.316%	$82.8834	$82.88	$82.90	$82.90
Purchase #3	$26.61	13.521%	$30.2079	$30.21	$30.20	$30.20
Purchase #4	$59.58	5.280%	$62.7258	$62.73	$62.75	$62.70
Purchase #5	$152.85	6.207%	$162.3374	$162.34	$162.35	$162.30
Purchase #6	$22.89	7.400%	$24.5839	$24.58	$24.60	$24.60
Purchase #7	$10.90	12.515%	$12.2641	$12.26	$12.25	$12.30
7 purchase totals =	$403.63		$436.7615	$436.76	$436.80	$436.80