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	$198.52	6.541%	$211.5052	$211.51	$211.50	$211.50
Purchase #2	$73.73	13.618%	$83.7706	$83.77	$83.75	$83.80
Purchase #3	$55.62	13.468%	$63.1109	$63.11	$63.10	$63.10
Purchase #4	$72.34	5.351%	$76.2109	$76.21	$76.20	$76.20
Purchase #5	$100.66	12.151%	$112.8912	$112.89	$112.90	$112.90
Purchase #6	$57.97	11.503%	$64.6383	$64.64	$64.65	$64.60
Purchase #7	$103.71	12.185%	$116.3471	$116.35	$116.35	$116.30
7 purchase totals =	$662.55		$728.4742	$728.48	$728.45	$728.40