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	$221.72	10.847%	$245.77	$245.77	$245.75	$245.80
Purchase #2	$176.89	7.262%	$189.7358	$189.74	$189.75	$189.70
Purchase #3	$90.71	4.413%	$94.713	$94.71	$94.70	$94.70
Purchase #4	$126.28	3.748%	$131.013	$131.01	$131.00	$131.00
Purchase #5	$116.90	4.231%	$121.846	$121.85	$121.85	$121.80
Purchase #6	$82.56	7.302%	$88.5885	$88.59	$88.60	$88.60
Purchase #7	$28.42	5.147%	$29.8828	$29.88	$29.90	$29.90
7 purchase totals =	$843.48		$901.5491	$901.55	$901.55	$901.50