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	$176.68	8.518%	$191.7296	$191.73	$191.75	$191.70
Purchase #2	$74.89	11.485%	$83.4911	$83.49	$83.50	$83.50
Purchase #3	$83.55	5.374%	$88.04	$88.04	$88.05	$88.00
Purchase #4	$35.48	5.866%	$37.5613	$37.56	$37.55	$37.60
Purchase #5	$96.94	12.858%	$109.4045	$109.40	$109.40	$109.40
Purchase #6	$80.47	4.214%	$83.861	$83.86	$83.85	$83.90
Purchase #7	$135.26	4.196%	$140.9355	$140.94	$140.95	$140.90
7 purchase totals =	$683.27		$735.0230	$735.02	$735.05	$735.00