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	$210.78	8.718%	$229.1558	$229.16	$229.15	$229.20
Purchase #2	$94.28	9.502%	$103.2385	$103.24	$103.25	$103.20
Purchase #3	$31.96	10.482%	$35.31	$35.31	$35.30	$35.30
Purchase #4	$152.98	13.276%	$173.2896	$173.29	$173.30	$173.30
Purchase #5	$71.47	9.271%	$78.096	$78.10	$78.10	$78.10
Purchase #6	$55.73	7.321%	$59.81	$59.81	$59.80	$59.80
Purchase #7	$40.98	7.792%	$44.1732	$44.17	$44.15	$44.20
7 purchase totals =	$658.18		$723.0731	$723.08	$723.05	$723.10