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	$91.98	5.726%	$97.2468	$97.25	$97.25	$97.20
Purchase #2	$41.60	8.647%	$45.1972	$45.20	$45.20	$45.20
Purchase #3	$62.96	13.873%	$71.6944	$71.69	$71.70	$71.70
Purchase #4	$154.73	10.399%	$170.8204	$170.82	$170.80	$170.80
Purchase #5	$15.42	13.226%	$17.4594	$17.46	$17.45	$17.50
Purchase #6	$85.56	6.133%	$90.8074	$90.81	$90.80	$90.80
Purchase #7	$86.54	5.260%	$91.092	$91.09	$91.10	$91.10
7 purchase totals =	$538.79		$584.3176	$584.32	$584.30	$584.30