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	$194.78	7.213%	$208.8295	$208.83	$208.85	$208.80
Purchase #2	$107.76	9.521%	$118.0198	$118.02	$118.00	$118.00
Purchase #3	$97.50	4.507%	$101.8943	$101.89	$101.90	$101.90
Purchase #4	$57.91	12.367%	$65.0717	$65.07	$65.05	$65.10
Purchase #5	$130.44	9.227%	$142.4757	$142.48	$142.50	$142.50
Purchase #6	$205.31	11.790%	$229.516	$229.52	$229.50	$229.50
Purchase #7	$126.44	7.588%	$136.0343	$136.03	$136.05	$136.00
7 purchase totals =	$920.14		$1,001.8413	$1,001.84	$1,001.85	$1,001.80