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	$237.88	10.208%	$262.1628	$262.16	$262.15	$262.20
Purchase #2	$88.69	13.580%	$100.7341	$100.73	$100.75	$100.70
Purchase #3	$87.69	11.689%	$97.9401	$97.94	$97.95	$97.90
Purchase #4	$220.30	12.639%	$248.1437	$248.14	$248.15	$248.10
Purchase #5	$29.86	5.296%	$31.4414	$31.44	$31.45	$31.40
Purchase #6	$65.59	3.478%	$67.8712	$67.87	$67.85	$67.90
Purchase #7	$168.44	10.330%	$185.8399	$185.84	$185.85	$185.80
7 purchase totals =	$898.45		$994.1332	$994.12	$994.15	$994.00