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	$55.66	9.405%	$60.8948	$60.89	$60.90	$60.90
Purchase #2	$92.61	8.227%	$100.229	$100.23	$100.25	$100.20
Purchase #3	$220.73	10.665%	$244.2709	$244.27	$244.25	$244.30
Purchase #4	$233.47	8.814%	$254.048	$254.05	$254.05	$254.00
Purchase #5	$25.94	4.276%	$27.0492	$27.05	$27.05	$27.00
Purchase #6	$19.48	9.109%	$21.2544	$21.25	$21.25	$21.30
Purchase #7	$44.88	7.449%	$48.2231	$48.22	$48.20	$48.20
7 purchase totals =	$692.77		$755.9694	$755.96	$755.95	$755.90