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	$179.33	12.312%	$201.4091	$201.41	$201.40	$201.40
Purchase #2	$151.98	8.858%	$165.4424	$165.44	$165.45	$165.40
Purchase #3	$215.53	10.776%	$238.7555	$238.76	$238.75	$238.80
Purchase #4	$199.88	6.704%	$213.28	$213.28	$213.30	$213.30
Purchase #5	$215.89	7.170%	$231.3693	$231.37	$231.35	$231.40
Purchase #6	$163.29	5.582%	$172.4048	$172.40	$172.40	$172.40
Purchase #7	$130.82	6.654%	$139.5248	$139.52	$139.50	$139.50
7 purchase totals =	$1,256.72		$1,362.1859	$1,362.18	$1,362.15	$1,362.20