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	$209.57	5.534%	$221.1676	$221.17	$221.15	$221.20
Purchase #2	$82.34	3.504%	$85.2252	$85.23	$85.25	$85.20
Purchase #3	$93.96	6.861%	$100.4066	$100.41	$100.40	$100.40
Purchase #4	$135.89	3.688%	$140.9016	$140.90	$140.90	$140.90
Purchase #5	$169.94	8.773%	$184.8488	$184.85	$184.85	$184.80
Purchase #6	$63.85	12.222%	$71.6537	$71.65	$71.65	$71.70
Purchase #7	$209.28	7.482%	$224.9383	$224.94	$224.95	$224.90
7 purchase totals =	$964.83		$1,029.1418	$1,029.15	$1,029.15	$1,029.10