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	$41.27	11.583%	$46.0503	$46.05	$46.05	$46.10
Purchase #2	$67.30	9.217%	$73.503	$73.50	$73.50	$73.50
Purchase #3	$26.70	9.863%	$29.3334	$29.33	$29.35	$29.30
Purchase #4	$129.92	9.163%	$141.8246	$141.82	$141.80	$141.80
Purchase #5	$6.62	10.618%	$7.3229	$7.32	$7.30	$7.30
Purchase #6	$49.49	8.212%	$53.5541	$53.55	$53.55	$53.60
Purchase #7	$188.82	4.269%	$196.8807	$196.88	$196.90	$196.90
7 purchase totals =	$510.12		$548.4690	$548.45	$548.45	$548.50