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	$212.55	12.261%	$238.6108	$238.61	$238.60	$238.60
Purchase #2	$67.73	3.641%	$70.196	$70.20	$70.20	$70.20
Purchase #3	$177.80	12.251%	$199.5823	$199.58	$199.60	$199.60
Purchase #4	$77.55	7.558%	$83.4112	$83.41	$83.40	$83.40
Purchase #5	$143.44	12.147%	$160.8637	$160.86	$160.85	$160.90
Purchase #6	$72.29	8.676%	$78.5619	$78.56	$78.55	$78.60
Purchase #7	$179.62	7.198%	$192.549	$192.55	$192.55	$192.50
7 purchase totals =	$930.98		$1,023.7749	$1,023.77	$1,023.75	$1,023.80