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	$163.88	5.298%	$172.5624	$172.56	$172.55	$172.60
Purchase #2	$202.27	11.648%	$225.8304	$225.83	$225.85	$225.80
Purchase #3	$79.32	13.241%	$89.8228	$89.82	$89.80	$89.80
Purchase #4	$175.32	8.583%	$190.3677	$190.37	$190.35	$190.40
Purchase #5	$37.98	8.810%	$41.326	$41.33	$41.35	$41.30
Purchase #6	$204.36	10.184%	$225.172	$225.17	$225.15	$225.20
Purchase #7	$59.37	9.499%	$65.0096	$65.01	$65.00	$65.00
7 purchase totals =	$922.50		$1,010.0909	$1,010.09	$1,010.05	$1,010.10