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	$159.72	9.845%	$175.4444	$175.44	$175.45	$175.40
Purchase #2	$91.37	9.470%	$100.0227	$100.02	$100.00	$100.00
Purchase #3	$146.47	4.277%	$152.7345	$152.73	$152.75	$152.70
Purchase #4	$219.79	4.479%	$229.6344	$229.63	$229.65	$229.60
Purchase #5	$219.62	9.202%	$239.8294	$239.83	$239.85	$239.80
Purchase #6	$67.42	6.650%	$71.9034	$71.90	$71.90	$71.90
Purchase #7	$84.94	12.421%	$95.4904	$95.49	$95.50	$95.50
7 purchase totals =	$989.33		$1,065.0592	$1,065.04	$1,065.10	$1,064.90