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	$124.75	5.616%	$131.756	$131.76	$131.75	$131.80
Purchase #2	$73.94	13.233%	$83.7245	$83.72	$83.70	$83.70
Purchase #3	$219.95	10.801%	$243.7068	$243.71	$243.70	$243.70
Purchase #4	$21.78	7.506%	$23.4148	$23.41	$23.40	$23.40
Purchase #5	$70.98	11.194%	$78.9255	$78.93	$78.95	$78.90
Purchase #6	$78.63	6.412%	$83.6718	$83.67	$83.65	$83.70
Purchase #7	$26.28	11.566%	$29.3195	$29.32	$29.30	$29.30
7 purchase totals =	$616.31		$674.5189	$674.52	$674.45	$674.50