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	$197.74	12.565%	$222.586	$222.59	$222.60	$222.60
Purchase #2	$148.28	11.461%	$165.2744	$165.27	$165.25	$165.30
Purchase #3	$225.45	8.554%	$244.735	$244.74	$244.75	$244.70
Purchase #4	$150.41	13.302%	$170.4175	$170.42	$170.40	$170.40
Purchase #5	$39.97	5.169%	$42.036	$42.04	$42.05	$42.00
Purchase #6	$28.81	12.846%	$32.5109	$32.51	$32.50	$32.50
Purchase #7	$157.48	4.157%	$164.0264	$164.03	$164.05	$164.00
7 purchase totals =	$948.14		$1,041.5862	$1,041.60	$1,041.60	$1,041.50