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	$201.91	8.700%	$219.4762	$219.48	$219.50	$219.50
Purchase #2	$88.86	7.276%	$95.3255	$95.33	$95.35	$95.30
Purchase #3	$18.42	11.565%	$20.5503	$20.55	$20.55	$20.60
Purchase #4	$155.89	7.227%	$167.1562	$167.16	$167.15	$167.20
Purchase #5	$42.86	11.102%	$47.6183	$47.62	$47.60	$47.60
Purchase #6	$131.37	12.345%	$147.5876	$147.59	$147.60	$147.60
Purchase #7	$130.74	11.708%	$146.047	$146.05	$146.05	$146.00
7 purchase totals =	$770.05		$843.7611	$843.78	$843.80	$843.80