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	$40.79	13.188%	$46.1694	$46.17	$46.15	$46.20
Purchase #2	$136.96	3.507%	$141.7632	$141.76	$141.75	$141.80
Purchase #3	$49.31	11.260%	$54.8623	$54.86	$54.85	$54.90
Purchase #4	$57.44	7.725%	$61.8772	$61.88	$61.90	$61.90
Purchase #5	$204.78	6.194%	$217.4641	$217.46	$217.45	$217.50
Purchase #6	$142.55	12.127%	$159.837	$159.84	$159.85	$159.80
Purchase #7	$130.79	7.813%	$141.0086	$141.01	$141.00	$141.00
7 purchase totals =	$762.62		$822.9818	$822.98	$822.95	$823.10