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	$98.52	4.556%	$103.0086	$103.01	$103.00	$103.00
Purchase #2	$230.93	13.844%	$262.8999	$262.90	$262.90	$262.90
Purchase #3	$185.60	13.203%	$210.1048	$210.10	$210.10	$210.10
Purchase #4	$37.30	6.374%	$39.6775	$39.68	$39.70	$39.70
Purchase #5	$102.61	4.160%	$106.8786	$106.88	$106.90	$106.90
Purchase #6	$198.38	7.325%	$212.9113	$212.91	$212.90	$212.90
Purchase #7	$69.61	12.124%	$78.0495	$78.05	$78.05	$78.00
7 purchase totals =	$922.95		$1,013.5302	$1,013.53	$1,013.55	$1,013.50