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	$89.47	13.323%	$101.3901	$101.39	$101.40	$101.40
Purchase #2	$115.51	4.639%	$120.8685	$120.87	$120.85	$120.90
Purchase #3	$81.30	10.549%	$89.8763	$89.88	$89.90	$89.90
Purchase #4	$205.75	12.618%	$231.7115	$231.71	$231.70	$231.70
Purchase #5	$237.46	6.866%	$253.764	$253.76	$253.75	$253.80
Purchase #6	$154.96	11.630%	$172.9818	$172.98	$173.00	$173.00
Purchase #7	$88.67	5.226%	$93.3039	$93.30	$93.30	$93.30
7 purchase totals =	$973.12		$1,063.8961	$1,063.89	$1,063.90	$1,064.00