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	$209.89	13.434%	$238.0866	$238.09	$238.10	$238.10
Purchase #2	$203.47	5.294%	$214.2417	$214.24	$214.25	$214.20
Purchase #3	$108.91	3.685%	$112.9233	$112.92	$112.90	$112.90
Purchase #4	$220.38	12.494%	$247.9143	$247.91	$247.90	$247.90
Purchase #5	$81.41	10.700%	$90.1209	$90.12	$90.10	$90.10
Purchase #6	$98.56	10.225%	$108.6378	$108.64	$108.65	$108.60
Purchase #7	$9.38	13.353%	$10.6325	$10.63	$10.65	$10.60
7 purchase totals =	$932.00		$1,022.5571	$1,022.55	$1,022.55	$1,022.40