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	$145.83	7.258%	$156.4143	$156.41	$156.40	$156.40
Purchase #2	$6.52	10.122%	$7.18	$7.18	$7.20	$7.20
Purchase #3	$36.26	13.150%	$41.0282	$41.03	$41.05	$41.00
Purchase #4	$147.43	13.555%	$167.4141	$167.41	$167.40	$167.40
Purchase #5	$189.99	13.379%	$215.4088	$215.41	$215.40	$215.40
Purchase #6	$172.69	8.304%	$187.0302	$187.03	$187.05	$187.00
Purchase #7	$53.47	11.770%	$59.7634	$59.76	$59.75	$59.80
7 purchase totals =	$752.19		$834.2390	$834.23	$834.25	$834.20