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	$216.91	5.185%	$228.1568	$228.16	$228.15	$228.20
Purchase #2	$112.48	13.867%	$128.0776	$128.08	$128.10	$128.10
Purchase #3	$136.85	7.374%	$146.9413	$146.94	$146.95	$146.90
Purchase #4	$97.79	8.315%	$105.9212	$105.92	$105.90	$105.90
Purchase #5	$91.83	4.366%	$95.8393	$95.84	$95.85	$95.80
Purchase #6	$52.45	12.769%	$59.1473	$59.15	$59.15	$59.10
Purchase #7	$193.25	8.540%	$209.7536	$209.75	$209.75	$209.80
7 purchase totals =	$901.56		$973.8371	$973.84	$973.85	$973.80