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	$151.26	13.298%	$171.3746	$171.37	$171.35	$171.40
Purchase #2	$153.77	4.497%	$160.685	$160.69	$160.70	$160.70
Purchase #3	$111.97	13.678%	$127.2853	$127.29	$127.30	$127.30
Purchase #4	$6.42	7.328%	$6.8905	$6.89	$6.90	$6.90
Purchase #5	$177.37	12.598%	$199.7151	$199.72	$199.70	$199.70
Purchase #6	$194.62	12.288%	$218.5349	$218.53	$218.55	$218.50
Purchase #7	$50.61	3.469%	$52.3657	$52.37	$52.35	$52.40
7 purchase totals =	$846.02		$936.8511	$936.86	$936.85	$936.90