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	$30.94	13.378%	$35.0792	$35.08	$35.10	$35.10
Purchase #2	$88.27	13.375%	$100.0761	$100.08	$100.10	$100.10
Purchase #3	$156.60	9.316%	$171.1889	$171.19	$171.20	$171.20
Purchase #4	$133.44	6.598%	$142.2444	$142.24	$142.25	$142.20
Purchase #5	$105.65	13.315%	$119.7173	$119.72	$119.70	$119.70
Purchase #6	$204.33	7.330%	$219.3074	$219.31	$219.30	$219.30
Purchase #7	$223.79	9.152%	$244.2713	$244.27	$244.25	$244.30
7 purchase totals =	$943.02		$1,031.8846	$1,031.89	$1,031.90	$1,031.90