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	$91.52	10.407%	$101.0445	$101.04	$101.05	$101.00
Purchase #2	$37.71	12.341%	$42.3638	$42.36	$42.35	$42.40
Purchase #3	$117.50	5.385%	$123.8274	$123.83	$123.85	$123.80
Purchase #4	$30.82	12.669%	$34.7246	$34.72	$34.70	$34.70
Purchase #5	$40.41	3.295%	$41.7415	$41.74	$41.75	$41.70
Purchase #6	$197.42	7.322%	$211.8751	$211.88	$211.90	$211.90
Purchase #7	$6.40	11.259%	$7.1206	$7.12	$7.10	$7.10
7 purchase totals =	$521.78		$562.6975	$562.69	$562.70	$562.60