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	$146.98	8.803%	$159.9186	$159.92	$159.90	$159.90
Purchase #2	$14.46	8.644%	$15.7099	$15.71	$15.70	$15.70
Purchase #3	$249.48	11.548%	$278.29	$278.29	$278.30	$278.30
Purchase #4	$92.76	8.699%	$100.8292	$100.83	$100.85	$100.80
Purchase #5	$91.56	6.517%	$97.527	$97.53	$97.55	$97.50
Purchase #6	$55.29	8.293%	$59.8752	$59.88	$59.90	$59.90
Purchase #7	$16.29	11.419%	$18.1502	$18.15	$18.15	$18.20
7 purchase totals =	$666.82		$730.3001	$730.31	$730.35	$730.30