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	$134.56	13.325%	$152.4901	$152.49	$152.50	$152.50
Purchase #2	$196.33	6.644%	$209.3742	$209.37	$209.35	$209.40
Purchase #3	$142.43	5.760%	$150.634	$150.63	$150.65	$150.60
Purchase #4	$233.96	3.458%	$242.0503	$242.05	$242.05	$242.10
Purchase #5	$197.77	3.162%	$204.0235	$204.02	$204.00	$204.00
Purchase #6	$59.43	9.851%	$65.2844	$65.28	$65.30	$65.30
Purchase #7	$36.81	12.648%	$41.4657	$41.47	$41.45	$41.50
7 purchase totals =	$1,001.29		$1,065.3222	$1,065.31	$1,065.30	$1,065.40