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	$219.53	6.439%	$233.6655	$233.67	$233.65	$233.70
Purchase #2	$113.77	12.277%	$127.7375	$127.74	$127.75	$127.70
Purchase #3	$216.38	11.857%	$242.0362	$242.04	$242.05	$242.00
Purchase #4	$120.49	9.462%	$131.8908	$131.89	$131.90	$131.90
Purchase #5	$50.60	6.596%	$53.9376	$53.94	$53.95	$53.90
Purchase #6	$5.47	11.536%	$6.101	$6.10	$6.10	$6.10
Purchase #7	$250.47	5.779%	$264.9447	$264.94	$264.95	$264.90
7 purchase totals =	$976.71		$1,060.3133	$1,060.32	$1,060.35	$1,060.20