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	$50.41	8.469%	$54.6792	$54.68	$54.70	$54.70
Purchase #2	$131.39	4.807%	$137.7059	$137.71	$137.70	$137.70
Purchase #3	$194.60	10.804%	$215.6246	$215.62	$215.60	$215.60
Purchase #4	$41.26	3.543%	$42.7218	$42.72	$42.70	$42.70
Purchase #5	$203.55	10.690%	$225.3095	$225.31	$225.30	$225.30
Purchase #6	$227.34	11.151%	$252.6907	$252.69	$252.70	$252.70
Purchase #7	$65.31	3.780%	$67.7787	$67.78	$67.80	$67.80
7 purchase totals =	$913.86		$996.5104	$996.51	$996.50	$996.50