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	$231.73	7.388%	$248.8502	$248.85	$248.85	$248.90
Purchase #2	$50.96	5.222%	$53.6211	$53.62	$53.60	$53.60
Purchase #3	$81.97	9.809%	$90.0104	$90.01	$90.00	$90.00
Purchase #4	$153.55	5.597%	$162.1442	$162.14	$162.15	$162.10
Purchase #5	$182.34	7.264%	$195.5852	$195.59	$195.60	$195.60
Purchase #6	$229.83	11.174%	$255.5112	$255.51	$255.50	$255.50
Purchase #7	$228.53	7.627%	$245.96	$245.96	$245.95	$246.00
7 purchase totals =	$1,158.91		$1,251.6823	$1,251.68	$1,251.65	$1,251.70