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	$39.93	13.356%	$45.2631	$45.26	$45.25	$45.30
Purchase #2	$187.63	6.237%	$199.3325	$199.33	$199.35	$199.30
Purchase #3	$213.41	4.656%	$223.3464	$223.35	$223.35	$223.30
Purchase #4	$150.66	6.147%	$159.9211	$159.92	$159.90	$159.90
Purchase #5	$93.68	6.162%	$99.4526	$99.45	$99.45	$99.50
Purchase #6	$39.75	4.130%	$41.3917	$41.39	$41.40	$41.40
Purchase #7	$171.99	9.393%	$188.145	$188.15	$188.15	$188.10
7 purchase totals =	$897.05		$956.8524	$956.85	$956.85	$956.80