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	$235.67	5.800%	$249.3389	$249.34	$249.35	$249.30
Purchase #2	$53.63	5.552%	$56.6075	$56.61	$56.60	$56.60
Purchase #3	$63.39	3.811%	$65.8058	$65.81	$65.80	$65.80
Purchase #4	$109.45	6.825%	$116.92	$116.92	$116.90	$116.90
Purchase #5	$169.32	7.672%	$182.3102	$182.31	$182.30	$182.30
Purchase #6	$72.93	13.681%	$82.9076	$82.91	$82.90	$82.90
Purchase #7	$229.55	5.279%	$241.6679	$241.67	$241.65	$241.70
7 purchase totals =	$933.94		$995.5579	$995.57	$995.50	$995.50