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	$72.27	3.730%	$74.9657	$74.97	$74.95	$75.00
Purchase #2	$44.59	13.746%	$50.7193	$50.72	$50.70	$50.70
Purchase #3	$181.26	8.605%	$196.8574	$196.86	$196.85	$196.90
Purchase #4	$102.50	8.854%	$111.5754	$111.58	$111.60	$111.60
Purchase #5	$238.72	12.165%	$267.7603	$267.76	$267.75	$267.80
Purchase #6	$180.27	13.426%	$204.4731	$204.47	$204.45	$204.50
Purchase #7	$191.63	3.389%	$198.1243	$198.12	$198.10	$198.10
7 purchase totals =	$1,011.24		$1,104.4755	$1,104.48	$1,104.40	$1,104.60