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	$123.80	3.607%	$128.2655	$128.27	$128.25	$128.30
Purchase #2	$109.86	4.853%	$115.1915	$115.19	$115.20	$115.20
Purchase #3	$35.89	10.325%	$39.5956	$39.60	$39.60	$39.60
Purchase #4	$199.57	13.256%	$226.025	$226.03	$226.05	$226.00
Purchase #5	$55.57	13.146%	$62.8752	$62.88	$62.90	$62.90
Purchase #6	$226.85	12.583%	$255.3945	$255.39	$255.40	$255.40
Purchase #7	$196.49	3.772%	$203.9016	$203.90	$203.90	$203.90
7 purchase totals =	$948.03		$1,031.2489	$1,031.26	$1,031.30	$1,031.30