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	$61.52	6.398%	$65.456	$65.46	$65.45	$65.50
Purchase #2	$188.55	11.779%	$210.7593	$210.76	$210.75	$210.80
Purchase #3	$170.93	8.262%	$185.0522	$185.05	$185.05	$185.10
Purchase #4	$207.46	7.419%	$222.8515	$222.85	$222.85	$222.90
Purchase #5	$84.70	8.793%	$92.1477	$92.15	$92.15	$92.10
Purchase #6	$129.64	6.665%	$138.2805	$138.28	$138.30	$138.30
Purchase #7	$220.31	4.551%	$230.3363	$230.34	$230.35	$230.30
7 purchase totals =	$1,063.11		$1,144.8835	$1,144.89	$1,144.90	$1,145.00