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	$192.48	9.410%	$210.5924	$210.59	$210.60	$210.60
Purchase #2	$48.46	7.785%	$52.2326	$52.23	$52.25	$52.20
Purchase #3	$90.94	11.200%	$101.1253	$101.13	$101.15	$101.10
Purchase #4	$163.79	6.785%	$174.9032	$174.90	$174.90	$174.90
Purchase #5	$17.67	4.785%	$18.5155	$18.52	$18.50	$18.50
Purchase #6	$85.61	7.137%	$91.72	$91.72	$91.70	$91.70
Purchase #7	$153.94	4.413%	$160.7334	$160.73	$160.75	$160.70
7 purchase totals =	$752.89		$809.8224	$809.82	$809.85	$809.70