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	$212.31	4.628%	$222.1357	$222.14	$222.15	$222.10
Purchase #2	$169.29	7.815%	$182.52	$182.52	$182.50	$182.50
Purchase #3	$77.70	10.338%	$85.7326	$85.73	$85.75	$85.70
Purchase #4	$82.88	3.182%	$85.5172	$85.52	$85.50	$85.50
Purchase #5	$28.89	6.339%	$30.7213	$30.72	$30.70	$30.70
Purchase #6	$153.81	5.761%	$162.671	$162.67	$162.65	$162.70
Purchase #7	$249.66	6.334%	$265.4735	$265.47	$265.45	$265.50
7 purchase totals =	$974.54		$1,034.7713	$1,034.77	$1,034.70	$1,034.70