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	$96.26	7.730%	$103.7009	$103.70	$103.70	$103.70
Purchase #2	$223.96	6.400%	$238.2934	$238.29	$238.30	$238.30
Purchase #3	$42.61	9.735%	$46.7581	$46.76	$46.75	$46.80
Purchase #4	$32.49	4.225%	$33.8627	$33.86	$33.85	$33.90
Purchase #5	$36.58	10.384%	$40.3785	$40.38	$40.40	$40.40
Purchase #6	$20.48	6.826%	$21.878	$21.88	$21.90	$21.90
Purchase #7	$39.53	5.324%	$41.6346	$41.63	$41.65	$41.60
7 purchase totals =	$491.91		$526.5062	$526.50	$526.55	$526.60