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	$183.32	6.217%	$194.717	$194.72	$194.70	$194.70
Purchase #2	$30.26	11.809%	$33.8334	$33.83	$33.85	$33.80
Purchase #3	$182.50	7.686%	$196.527	$196.53	$196.55	$196.50
Purchase #4	$43.56	12.148%	$48.8517	$48.85	$48.85	$48.90
Purchase #5	$223.30	3.792%	$231.7675	$231.77	$231.75	$231.80
Purchase #6	$97.70	8.176%	$105.688	$105.69	$105.70	$105.70
Purchase #7	$95.27	6.347%	$101.3168	$101.32	$101.30	$101.30
7 purchase totals =	$855.91		$912.7014	$912.71	$912.70	$912.70