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	$147.40	9.451%	$161.3308	$161.33	$161.35	$161.30
Purchase #2	$71.61	9.245%	$78.2303	$78.23	$78.25	$78.20
Purchase #3	$120.65	4.712%	$126.335	$126.34	$126.35	$126.30
Purchase #4	$74.89	5.211%	$78.7925	$78.79	$78.80	$78.80
Purchase #5	$115.55	11.445%	$128.7747	$128.77	$128.75	$128.80
Purchase #6	$131.25	4.765%	$137.5041	$137.50	$137.50	$137.50
Purchase #7	$54.87	4.433%	$57.3024	$57.30	$57.30	$57.30
7 purchase totals =	$716.22		$768.2698	$768.26	$768.30	$768.20