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	$83.56	12.857%	$94.3033	$94.30	$94.30	$94.30
Purchase #2	$113.46	12.359%	$127.4825	$127.48	$127.50	$127.50
Purchase #3	$18.73	11.414%	$20.8678	$20.87	$20.85	$20.90
Purchase #4	$176.85	10.832%	$196.0064	$196.01	$196.00	$196.00
Purchase #5	$10.36	10.151%	$11.4116	$11.41	$11.40	$11.40
Purchase #6	$108.98	10.204%	$120.1003	$120.10	$120.10	$120.10
Purchase #7	$40.49	10.534%	$44.7552	$44.76	$44.75	$44.80
7 purchase totals =	$552.43		$614.9271	$614.93	$614.90	$615.00