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	$159.52	11.320%	$177.5777	$177.58	$177.60	$177.60
Purchase #2	$190.82	13.323%	$216.2429	$216.24	$216.25	$216.20
Purchase #3	$231.29	5.211%	$243.3425	$243.34	$243.35	$243.30
Purchase #4	$97.97	10.764%	$108.5155	$108.52	$108.50	$108.50
Purchase #5	$71.97	13.405%	$81.6176	$81.62	$81.60	$81.60
Purchase #6	$211.45	5.538%	$223.1601	$223.16	$223.15	$223.20
Purchase #7	$90.46	10.603%	$100.0515	$100.05	$100.05	$100.10
7 purchase totals =	$1,053.48		$1,150.5078	$1,150.51	$1,150.50	$1,150.50