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	$194.35	7.829%	$209.5657	$209.57	$209.55	$209.60
Purchase #2	$215.83	12.477%	$242.7591	$242.76	$242.75	$242.80
Purchase #3	$19.37	7.493%	$20.8214	$20.82	$20.80	$20.80
Purchase #4	$134.46	13.640%	$152.8003	$152.80	$152.80	$152.80
Purchase #5	$247.79	6.602%	$264.1491	$264.15	$264.15	$264.10
Purchase #6	$205.28	8.577%	$222.8869	$222.89	$222.90	$222.90
Purchase #7	$147.88	13.272%	$167.5066	$167.51	$167.50	$167.50
7 purchase totals =	$1,164.96		$1,280.4891	$1,280.50	$1,280.45	$1,280.50