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	$236.64	13.215%	$267.912	$267.91	$267.90	$267.90
Purchase #2	$35.39	6.379%	$37.6475	$37.65	$37.65	$37.60
Purchase #3	$156.45	8.421%	$169.6247	$169.62	$169.60	$169.60
Purchase #4	$24.61	8.603%	$26.7272	$26.73	$26.75	$26.70
Purchase #5	$82.70	6.814%	$88.3352	$88.34	$88.35	$88.30
Purchase #6	$11.34	13.727%	$12.8966	$12.90	$12.90	$12.90
Purchase #7	$118.27	4.250%	$123.2965	$123.30	$123.30	$123.30
7 purchase totals =	$665.40		$726.4397	$726.45	$726.45	$726.30