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	$146.56	12.568%	$164.9797	$164.98	$165.00	$165.00
Purchase #2	$137.66	9.134%	$150.2339	$150.23	$150.25	$150.20
Purchase #3	$39.67	3.107%	$40.9025	$40.90	$40.90	$40.90
Purchase #4	$49.66	4.118%	$51.705	$51.71	$51.70	$51.70
Purchase #5	$225.73	6.406%	$240.1903	$240.19	$240.20	$240.20
Purchase #6	$194.60	13.331%	$220.5421	$220.54	$220.55	$220.50
Purchase #7	$240.67	6.243%	$255.695	$255.70	$255.70	$255.70
7 purchase totals =	$1,034.55		$1,124.2485	$1,124.25	$1,124.30	$1,124.20