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	$160.32	4.422%	$167.4094	$167.41	$167.40	$167.40
Purchase #2	$178.53	5.783%	$188.8544	$188.85	$188.85	$188.90
Purchase #3	$78.39	13.705%	$89.1333	$89.13	$89.15	$89.10
Purchase #4	$106.57	13.104%	$120.5349	$120.53	$120.55	$120.50
Purchase #5	$50.28	10.113%	$55.3648	$55.36	$55.35	$55.40
Purchase #6	$68.45	10.863%	$75.8857	$75.89	$75.90	$75.90
Purchase #7	$212.65	11.607%	$237.3323	$237.33	$237.35	$237.30
7 purchase totals =	$855.19		$934.5148	$934.50	$934.55	$934.50