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	$89.96	8.344%	$97.4663	$97.47	$97.45	$97.50
Purchase #2	$198.90	12.550%	$223.862	$223.86	$223.85	$223.90
Purchase #3	$173.33	6.743%	$185.0176	$185.02	$185.00	$185.00
Purchase #4	$147.88	12.780%	$166.7791	$166.78	$166.80	$166.80
Purchase #5	$148.57	4.378%	$155.0744	$155.07	$155.05	$155.10
Purchase #6	$94.70	4.668%	$99.1206	$99.12	$99.10	$99.10
Purchase #7	$147.81	11.363%	$164.6057	$164.61	$164.60	$164.60
7 purchase totals =	$1,001.15		$1,091.9257	$1,091.93	$1,091.85	$1,092.00