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	$53.94	12.252%	$60.5487	$60.55	$60.55	$60.50
Purchase #2	$150.96	3.816%	$156.7206	$156.72	$156.70	$156.70
Purchase #3	$203.42	9.457%	$222.6574	$222.66	$222.65	$222.70
Purchase #4	$55.56	11.417%	$61.9033	$61.90	$61.90	$61.90
Purchase #5	$194.81	7.357%	$209.1422	$209.14	$209.15	$209.10
Purchase #6	$57.53	10.791%	$63.7381	$63.74	$63.75	$63.70
Purchase #7	$206.50	12.865%	$233.0662	$233.07	$233.05	$233.10
7 purchase totals =	$922.72		$1,007.7765	$1,007.78	$1,007.75	$1,007.70