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	$216.69	12.328%	$243.4035	$243.40	$243.40	$243.40
Purchase #2	$29.92	10.157%	$32.959	$32.96	$32.95	$33.00
Purchase #3	$172.96	13.699%	$196.6538	$196.65	$196.65	$196.70
Purchase #4	$67.91	6.865%	$72.572	$72.57	$72.55	$72.60
Purchase #5	$169.61	12.868%	$191.4354	$191.44	$191.45	$191.40
Purchase #6	$120.37	13.402%	$136.502	$136.50	$136.50	$136.50
Purchase #7	$234.56	5.618%	$247.7376	$247.74	$247.75	$247.70
7 purchase totals =	$1,012.02		$1,121.2633	$1,121.26	$1,121.25	$1,121.30