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	$85.29	6.405%	$90.7528	$90.75	$90.75	$90.80
Purchase #2	$35.31	6.583%	$37.6345	$37.63	$37.65	$37.60
Purchase #3	$169.89	4.104%	$176.8623	$176.86	$176.85	$176.90
Purchase #4	$49.72	7.736%	$53.5663	$53.57	$53.55	$53.60
Purchase #5	$30.27	13.641%	$34.3991	$34.40	$34.40	$34.40
Purchase #6	$23.72	8.118%	$25.6456	$25.65	$25.65	$25.60
Purchase #7	$50.75	7.257%	$54.4329	$54.43	$54.45	$54.40
7 purchase totals =	$444.95		$473.2935	$473.29	$473.30	$473.30