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	$149.73	9.734%	$164.3047	$164.30	$164.30	$164.30
Purchase #2	$143.83	4.460%	$150.2448	$150.24	$150.25	$150.20
Purchase #3	$75.76	3.830%	$78.6616	$78.66	$78.65	$78.70
Purchase #4	$112.56	8.161%	$121.746	$121.75	$121.75	$121.70
Purchase #5	$171.48	9.111%	$187.1035	$187.10	$187.10	$187.10
Purchase #6	$53.67	9.854%	$58.9586	$58.96	$58.95	$59.00
Purchase #7	$241.47	6.288%	$256.6536	$256.65	$256.65	$256.70
7 purchase totals =	$948.50		$1,017.6728	$1,017.66	$1,017.65	$1,017.70