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	$187.26	12.204%	$210.1132	$210.11	$210.10	$210.10
Purchase #2	$198.63	11.870%	$222.2074	$222.21	$222.20	$222.20
Purchase #3	$226.82	3.228%	$234.1417	$234.14	$234.15	$234.10
Purchase #4	$32.27	11.488%	$35.9772	$35.98	$36.00	$36.00
Purchase #5	$19.40	7.536%	$20.862	$20.86	$20.85	$20.90
Purchase #6	$91.71	9.572%	$100.4885	$100.49	$100.50	$100.50
Purchase #7	$67.83	5.688%	$71.6882	$71.69	$71.70	$71.70
7 purchase totals =	$823.92		$895.4782	$895.48	$895.50	$895.50