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	$82.66	10.834%	$91.6154	$91.62	$91.60	$91.60
Purchase #2	$225.25	11.584%	$251.343	$251.34	$251.35	$251.30
Purchase #3	$148.78	12.535%	$167.4296	$167.43	$167.45	$167.40
Purchase #4	$239.50	3.174%	$247.1017	$247.10	$247.10	$247.10
Purchase #5	$29.30	13.281%	$33.1913	$33.19	$33.20	$33.20
Purchase #6	$222.77	8.807%	$242.3894	$242.39	$242.40	$242.40
Purchase #7	$88.43	6.691%	$94.3469	$94.35	$94.35	$94.30
7 purchase totals =	$1,036.69		$1,127.4173	$1,127.42	$1,127.45	$1,127.30