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	$202.73	9.790%	$222.5773	$222.58	$222.60	$222.60
Purchase #2	$31.46	6.523%	$33.5121	$33.51	$33.50	$33.50
Purchase #3	$167.97	11.551%	$187.3722	$187.37	$187.35	$187.40
Purchase #4	$165.89	6.307%	$176.3527	$176.35	$176.35	$176.40
Purchase #5	$238.61	10.456%	$263.5591	$263.56	$263.55	$263.60
Purchase #6	$128.32	12.831%	$144.7847	$144.78	$144.80	$144.80
Purchase #7	$86.55	9.498%	$94.7705	$94.77	$94.75	$94.80
7 purchase totals =	$1,021.53		$1,122.9286	$1,122.92	$1,122.90	$1,123.10