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	$240.57	7.428%	$258.4395	$258.44	$258.45	$258.40
Purchase #2	$90.62	13.445%	$102.8039	$102.80	$102.80	$102.80
Purchase #3	$68.88	13.290%	$78.0342	$78.03	$78.05	$78.00
Purchase #4	$118.55	4.119%	$123.4331	$123.43	$123.45	$123.40
Purchase #5	$58.88	12.472%	$66.2235	$66.22	$66.20	$66.20
Purchase #6	$130.54	7.446%	$140.26	$140.26	$140.25	$140.30
Purchase #7	$233.61	8.549%	$253.5813	$253.58	$253.60	$253.60
7 purchase totals =	$941.65		$1,022.7755	$1,022.76	$1,022.80	$1,022.70