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	$215.78	12.553%	$242.8669	$242.87	$242.85	$242.90
Purchase #2	$161.49	12.863%	$182.2625	$182.26	$182.25	$182.30
Purchase #3	$121.28	10.114%	$133.5463	$133.55	$133.55	$133.50
Purchase #4	$87.87	13.549%	$99.7755	$99.78	$99.80	$99.80
Purchase #5	$175.29	13.280%	$198.5685	$198.57	$198.55	$198.60
Purchase #6	$68.72	13.744%	$78.1649	$78.16	$78.15	$78.20
Purchase #7	$131.84	9.639%	$144.5481	$144.55	$144.55	$144.50
7 purchase totals =	$962.27		$1,079.7327	$1,079.74	$1,079.70	$1,079.80