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	$166.47	3.242%	$171.867	$171.87	$171.85	$171.90
Purchase #2	$247.52	5.664%	$261.5395	$261.54	$261.55	$261.50
Purchase #3	$197.32	11.510%	$220.0315	$220.03	$220.05	$220.00
Purchase #4	$16.54	12.291%	$18.5729	$18.57	$18.55	$18.60
Purchase #5	$233.71	7.164%	$250.453	$250.45	$250.45	$250.50
Purchase #6	$141.56	4.814%	$148.3747	$148.37	$148.35	$148.40
Purchase #7	$147.34	5.423%	$155.3302	$155.33	$155.35	$155.30
7 purchase totals =	$1,150.46		$1,226.1688	$1,226.16	$1,226.15	$1,226.20