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	$96.72	6.111%	$102.6306	$102.63	$102.65	$102.60
Purchase #2	$199.48	8.109%	$215.6558	$215.66	$215.65	$215.70
Purchase #3	$85.88	4.344%	$89.6106	$89.61	$89.60	$89.60
Purchase #4	$179.38	13.463%	$203.5299	$203.53	$203.55	$203.50
Purchase #5	$75.40	10.840%	$83.5734	$83.57	$83.55	$83.60
Purchase #6	$157.30	9.412%	$172.1051	$172.11	$172.10	$172.10
Purchase #7	$205.28	10.588%	$227.015	$227.02	$227.00	$227.00
7 purchase totals =	$999.44		$1,094.1204	$1,094.13	$1,094.10	$1,094.10