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	$93.69	10.281%	$103.3223	$103.32	$103.30	$103.30
Purchase #2	$192.78	12.798%	$217.452	$217.45	$217.45	$217.50
Purchase #3	$223.29	7.603%	$240.2667	$240.27	$240.25	$240.30
Purchase #4	$145.40	7.577%	$156.417	$156.42	$156.40	$156.40
Purchase #5	$85.65	6.634%	$91.332	$91.33	$91.35	$91.30
Purchase #6	$132.65	7.758%	$142.941	$142.94	$142.95	$142.90
Purchase #7	$218.45	11.761%	$244.1419	$244.14	$244.15	$244.10
7 purchase totals =	$1,091.91		$1,195.8729	$1,195.87	$1,195.85	$1,195.80