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	$196.91	13.314%	$223.1266	$223.13	$223.15	$223.10
Purchase #2	$53.49	7.305%	$57.3974	$57.40	$57.40	$57.40
Purchase #3	$147.66	6.384%	$157.0866	$157.09	$157.10	$157.10
Purchase #4	$187.69	4.559%	$196.2468	$196.25	$196.25	$196.20
Purchase #5	$97.41	9.393%	$106.5597	$106.56	$106.55	$106.60
Purchase #6	$211.80	12.797%	$238.904	$238.90	$238.90	$238.90
Purchase #7	$32.50	10.200%	$35.815	$35.82	$35.80	$35.80
7 purchase totals =	$927.46		$1,015.1361	$1,015.15	$1,015.15	$1,015.10