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	$41.44	10.395%	$45.7477	$45.75	$45.75	$45.70
Purchase #2	$86.57	10.290%	$95.4781	$95.48	$95.50	$95.50
Purchase #3	$223.71	11.762%	$250.0228	$250.02	$250.00	$250.00
Purchase #4	$134.72	11.492%	$150.202	$150.20	$150.20	$150.20
Purchase #5	$12.60	10.603%	$13.936	$13.94	$13.95	$13.90
Purchase #6	$102.40	11.434%	$114.1084	$114.11	$114.10	$114.10
Purchase #7	$222.35	10.237%	$245.112	$245.11	$245.10	$245.10
7 purchase totals =	$823.79		$914.6070	$914.61	$914.60	$914.50