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	$172.57	11.173%	$191.8512	$191.85	$191.85	$191.90
Purchase #2	$146.98	12.634%	$165.5495	$165.55	$165.55	$165.50
Purchase #3	$220.81	3.439%	$228.4037	$228.40	$228.40	$228.40
Purchase #4	$99.73	11.492%	$111.191	$111.19	$111.20	$111.20
Purchase #5	$226.46	8.357%	$245.3853	$245.39	$245.40	$245.40
Purchase #6	$73.57	9.605%	$80.6364	$80.64	$80.65	$80.60
Purchase #7	$227.80	13.761%	$259.1476	$259.15	$259.15	$259.10
7 purchase totals =	$1,167.92		$1,282.1647	$1,282.17	$1,282.20	$1,282.10