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	$137.63	13.452%	$156.144	$156.14	$156.15	$156.10
Purchase #2	$33.57	11.350%	$37.3802	$37.38	$37.40	$37.40
Purchase #3	$218.44	9.107%	$238.3333	$238.33	$238.35	$238.30
Purchase #4	$227.38	7.662%	$244.8019	$244.80	$244.80	$244.80
Purchase #5	$238.95	13.638%	$271.538	$271.54	$271.55	$271.50
Purchase #6	$143.83	3.254%	$148.5102	$148.51	$148.50	$148.50
Purchase #7	$20.65	9.403%	$22.5917	$22.59	$22.60	$22.60
7 purchase totals =	$1,020.45		$1,119.2993	$1,119.29	$1,119.35	$1,119.20