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	$40.29	13.799%	$45.8496	$45.85	$45.85	$45.80
Purchase #2	$119.71	7.124%	$128.2381	$128.24	$128.25	$128.20
Purchase #3	$220.78	4.333%	$230.3464	$230.35	$230.35	$230.30
Purchase #4	$92.61	10.250%	$102.1025	$102.10	$102.10	$102.10
Purchase #5	$182.53	3.231%	$188.4275	$188.43	$188.45	$188.40
Purchase #6	$101.36	7.811%	$109.2772	$109.28	$109.30	$109.30
Purchase #7	$191.52	6.754%	$204.4553	$204.46	$204.45	$204.50
7 purchase totals =	$948.80		$1,008.6966	$1,008.71	$1,008.75	$1,008.60