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	$187.61	5.822%	$198.5327	$198.53	$198.55	$198.50
Purchase #2	$223.33	5.290%	$235.1442	$235.14	$235.15	$235.10
Purchase #3	$209.74	4.331%	$218.8238	$218.82	$218.80	$218.80
Purchase #4	$198.98	11.492%	$221.8468	$221.85	$221.85	$221.80
Purchase #5	$188.85	3.868%	$196.1547	$196.15	$196.15	$196.20
Purchase #6	$219.68	4.157%	$228.8121	$228.81	$228.80	$228.80
Purchase #7	$243.45	13.131%	$275.4174	$275.42	$275.40	$275.40
7 purchase totals =	$1,471.64		$1,574.7317	$1,574.72	$1,574.70	$1,574.60