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	$150.31	11.171%	$167.1011	$167.10	$167.10	$167.10
Purchase #2	$62.89	11.526%	$70.1387	$70.14	$70.15	$70.10
Purchase #3	$33.86	11.376%	$37.7119	$37.71	$37.70	$37.70
Purchase #4	$9.37	12.838%	$10.5729	$10.57	$10.55	$10.60
Purchase #5	$18.80	6.674%	$20.0547	$20.05	$20.05	$20.10
Purchase #6	$47.85	3.565%	$49.5559	$49.56	$49.55	$49.60
Purchase #7	$155.33	8.376%	$168.3404	$168.34	$168.35	$168.30
7 purchase totals =	$478.41		$523.4756	$523.47	$523.45	$523.50