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	$191.84	11.172%	$213.2724	$213.27	$213.25	$213.30
Purchase #2	$41.83	9.548%	$45.8239	$45.82	$45.80	$45.80
Purchase #3	$89.53	9.845%	$98.3442	$98.34	$98.35	$98.30
Purchase #4	$36.61	7.564%	$39.3792	$39.38	$39.40	$39.40
Purchase #5	$154.63	10.173%	$170.3605	$170.36	$170.35	$170.40
Purchase #6	$185.74	7.667%	$199.9807	$199.98	$200.00	$200.00
Purchase #7	$42.99	12.186%	$48.2288	$48.23	$48.25	$48.20
7 purchase totals =	$743.17		$815.3897	$815.38	$815.40	$815.40