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	$223.94	3.872%	$232.611	$232.61	$232.60	$232.60
Purchase #2	$180.59	7.760%	$194.6038	$194.60	$194.60	$194.60
Purchase #3	$101.66	3.551%	$105.2699	$105.27	$105.25	$105.30
Purchase #4	$103.65	10.522%	$114.5561	$114.56	$114.55	$114.60
Purchase #5	$43.77	6.663%	$46.6864	$46.69	$46.70	$46.70
Purchase #6	$36.49	13.154%	$41.2899	$41.29	$41.30	$41.30
Purchase #7	$79.89	13.220%	$90.4515	$90.45	$90.45	$90.50
7 purchase totals =	$769.99		$825.4686	$825.47	$825.45	$825.60