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	$154.56	5.389%	$162.8892	$162.89	$162.90	$162.90
Purchase #2	$235.90	4.435%	$246.3622	$246.36	$246.35	$246.40
Purchase #3	$155.32	11.601%	$173.3387	$173.34	$173.35	$173.30
Purchase #4	$36.33	3.118%	$37.4628	$37.46	$37.45	$37.50
Purchase #5	$95.46	10.831%	$105.7993	$105.80	$105.80	$105.80
Purchase #6	$64.31	9.433%	$70.3764	$70.38	$70.40	$70.40
Purchase #7	$233.94	7.425%	$251.31	$251.31	$251.30	$251.30
7 purchase totals =	$975.82		$1,047.5386	$1,047.54	$1,047.55	$1,047.60