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	$28.34	13.868%	$32.2702	$32.27	$32.25	$32.30
Purchase #2	$126.25	12.681%	$142.2598	$142.26	$142.25	$142.30
Purchase #3	$18.73	10.609%	$20.7171	$20.72	$20.70	$20.70
Purchase #4	$75.48	12.547%	$84.9505	$84.95	$84.95	$85.00
Purchase #5	$54.85	8.147%	$59.3186	$59.32	$59.30	$59.30
Purchase #6	$67.45	9.368%	$73.7687	$73.77	$73.75	$73.80
Purchase #7	$222.56	11.496%	$248.1455	$248.15	$248.15	$248.10
7 purchase totals =	$593.66		$661.4304	$661.44	$661.35	$661.50