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	$29.47	11.155%	$32.7574	$32.76	$32.75	$32.80
Purchase #2	$246.78	3.553%	$255.5481	$255.55	$255.55	$255.50
Purchase #3	$130.29	9.713%	$142.9451	$142.95	$142.95	$142.90
Purchase #4	$19.46	11.721%	$21.7409	$21.74	$21.75	$21.70
Purchase #5	$177.40	10.422%	$195.8886	$195.89	$195.90	$195.90
Purchase #6	$206.99	7.722%	$222.9738	$222.97	$222.95	$223.00
Purchase #7	$198.79	5.277%	$209.2801	$209.28	$209.30	$209.30
7 purchase totals =	$1,009.18		$1,081.1340	$1,081.14	$1,081.15	$1,081.10