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	$165.54	3.820%	$171.8636	$171.86	$171.85	$171.90
Purchase #2	$241.60	9.588%	$264.7646	$264.76	$264.75	$264.80
Purchase #3	$207.60	8.732%	$225.7276	$225.73	$225.75	$225.70
Purchase #4	$31.90	8.487%	$34.6074	$34.61	$34.60	$34.60
Purchase #5	$104.26	13.541%	$118.3778	$118.38	$118.40	$118.40
Purchase #6	$115.67	10.154%	$127.4151	$127.42	$127.40	$127.40
Purchase #7	$116.80	11.307%	$130.0066	$130.01	$130.00	$130.00
7 purchase totals =	$983.37		$1,072.7627	$1,072.77	$1,072.75	$1,072.80