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	$230.67	10.524%	$254.9457	$254.95	$254.95	$254.90
Purchase #2	$54.96	8.140%	$59.4337	$59.43	$59.45	$59.40
Purchase #3	$190.61	13.658%	$216.6435	$216.64	$216.65	$216.60
Purchase #4	$41.45	11.735%	$46.3142	$46.31	$46.30	$46.30
Purchase #5	$222.46	7.814%	$239.843	$239.84	$239.85	$239.80
Purchase #6	$130.65	12.200%	$146.5893	$146.59	$146.60	$146.60
Purchase #7	$62.40	12.518%	$70.2112	$70.21	$70.20	$70.20
7 purchase totals =	$933.20		$1,033.9806	$1,033.97	$1,034.00	$1,033.80