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	$76.26	5.545%	$80.4886	$80.49	$80.50	$80.50
Purchase #2	$158.62	12.433%	$178.3412	$178.34	$178.35	$178.30
Purchase #3	$229.73	12.530%	$258.5152	$258.52	$258.50	$258.50
Purchase #4	$95.37	5.653%	$100.7613	$100.76	$100.75	$100.80
Purchase #5	$220.51	9.682%	$241.8598	$241.86	$241.85	$241.90
Purchase #6	$139.39	9.611%	$152.7868	$152.79	$152.80	$152.80
Purchase #7	$28.88	11.180%	$32.1088	$32.11	$32.10	$32.10
7 purchase totals =	$948.76		$1,044.8617	$1,044.87	$1,044.85	$1,044.90