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	$189.33	9.363%	$207.057	$207.06	$207.05	$207.10
Purchase #2	$223.89	6.418%	$238.2593	$238.26	$238.25	$238.30
Purchase #3	$195.25	8.501%	$211.8482	$211.85	$211.85	$211.80
Purchase #4	$130.85	6.426%	$139.2584	$139.26	$139.25	$139.30
Purchase #5	$17.82	11.747%	$19.9133	$19.91	$19.90	$19.90
Purchase #6	$243.86	10.816%	$270.2359	$270.24	$270.25	$270.20
Purchase #7	$62.52	4.497%	$65.3315	$65.33	$65.35	$65.30
7 purchase totals =	$1,063.52		$1,151.9036	$1,151.91	$1,151.90	$1,151.90