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	$69.52	13.180%	$78.6827	$78.68	$78.70	$78.70
Purchase #2	$138.46	4.842%	$145.1642	$145.16	$145.15	$145.20
Purchase #3	$188.55	9.534%	$206.5264	$206.53	$206.55	$206.50
Purchase #4	$84.36	11.871%	$94.3744	$94.37	$94.35	$94.40
Purchase #5	$141.38	6.869%	$151.0914	$151.09	$151.10	$151.10
Purchase #6	$247.54	8.728%	$269.1453	$269.15	$269.15	$269.10
Purchase #7	$70.65	9.200%	$77.1498	$77.15	$77.15	$77.10
7 purchase totals =	$940.46		$1,022.1342	$1,022.13	$1,022.15	$1,022.10