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	$174.47	12.674%	$196.5823	$196.58	$196.60	$196.60
Purchase #2	$108.72	13.218%	$123.0906	$123.09	$123.10	$123.10
Purchase #3	$134.54	9.790%	$147.7115	$147.71	$147.70	$147.70
Purchase #4	$37.39	11.166%	$41.565	$41.57	$41.55	$41.60
Purchase #5	$195.90	12.318%	$220.031	$220.03	$220.05	$220.00
Purchase #6	$131.72	6.793%	$140.6677	$140.67	$140.65	$140.70
Purchase #7	$231.54	9.696%	$253.9901	$253.99	$254.00	$254.00
7 purchase totals =	$1,014.28		$1,123.6382	$1,123.64	$1,123.65	$1,123.70