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	$133.68	11.233%	$148.6963	$148.70	$148.70	$148.70
Purchase #2	$213.33	3.768%	$221.3683	$221.37	$221.35	$221.40
Purchase #3	$93.72	4.837%	$98.2532	$98.25	$98.25	$98.30
Purchase #4	$185.46	6.129%	$196.8268	$196.83	$196.85	$196.80
Purchase #5	$151.72	3.574%	$157.1425	$157.14	$157.15	$157.10
Purchase #6	$197.43	12.391%	$221.8936	$221.89	$221.90	$221.90
Purchase #7	$71.43	12.318%	$80.2287	$80.23	$80.25	$80.20
7 purchase totals =	$1,046.77		$1,124.4094	$1,124.41	$1,124.45	$1,124.40