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	$101.31	7.521%	$108.9295	$108.93	$108.95	$108.90
Purchase #2	$48.69	11.233%	$54.1593	$54.16	$54.15	$54.20
Purchase #3	$82.75	8.753%	$89.9931	$89.99	$90.00	$90.00
Purchase #4	$89.48	10.704%	$99.0579	$99.06	$99.05	$99.10
Purchase #5	$124.46	12.228%	$139.679	$139.68	$139.70	$139.70
Purchase #6	$172.61	12.781%	$194.6713	$194.67	$194.65	$194.70
Purchase #7	$45.42	8.601%	$49.3266	$49.33	$49.35	$49.30
7 purchase totals =	$664.72		$735.8167	$735.82	$735.85	$735.90