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	$138.78	4.502%	$145.0279	$145.03	$145.05	$145.00
Purchase #2	$195.71	4.483%	$204.4837	$204.48	$204.50	$204.50
Purchase #3	$74.45	10.492%	$82.2613	$82.26	$82.25	$82.30
Purchase #4	$114.91	4.325%	$119.8799	$119.88	$119.90	$119.90
Purchase #5	$51.85	6.328%	$55.1311	$55.13	$55.15	$55.10
Purchase #6	$212.36	10.809%	$235.314	$235.31	$235.30	$235.30
Purchase #7	$35.28	11.576%	$39.364	$39.36	$39.35	$39.40
7 purchase totals =	$823.34		$881.4619	$881.45	$881.50	$881.50