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	$57.42	3.711%	$59.5509	$59.55	$59.55	$59.60
Purchase #2	$143.82	9.642%	$157.6871	$157.69	$157.70	$157.70
Purchase #3	$184.88	6.303%	$196.533	$196.53	$196.55	$196.50
Purchase #4	$221.98	7.730%	$239.1391	$239.14	$239.15	$239.10
Purchase #5	$9.96	12.487%	$11.2037	$11.20	$11.20	$11.20
Purchase #6	$145.73	13.459%	$165.3438	$165.34	$165.35	$165.30
Purchase #7	$178.49	9.732%	$195.8606	$195.86	$195.85	$195.90
7 purchase totals =	$942.28		$1,025.3182	$1,025.31	$1,025.35	$1,025.30