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	$53.32	12.366%	$59.9136	$59.91	$59.90	$59.90
Purchase #2	$196.83	6.556%	$209.7342	$209.73	$209.75	$209.70
Purchase #3	$92.63	7.286%	$99.379	$99.38	$99.40	$99.40
Purchase #4	$106.42	13.211%	$120.4791	$120.48	$120.50	$120.50
Purchase #5	$97.34	11.245%	$108.2859	$108.29	$108.30	$108.30
Purchase #6	$127.46	8.436%	$138.2125	$138.21	$138.20	$138.20
Purchase #7	$169.73	9.382%	$185.6541	$185.65	$185.65	$185.70
7 purchase totals =	$843.73		$921.6584	$921.65	$921.70	$921.70