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	$46.95	11.851%	$52.514	$52.51	$52.50	$52.50
Purchase #2	$85.57	13.708%	$97.2999	$97.30	$97.30	$97.30
Purchase #3	$54.42	5.866%	$57.6123	$57.61	$57.60	$57.60
Purchase #4	$221.92	7.353%	$238.2378	$238.24	$238.25	$238.20
Purchase #5	$34.42	3.156%	$35.5063	$35.51	$35.50	$35.50
Purchase #6	$243.79	6.177%	$258.8489	$258.85	$258.85	$258.80
Purchase #7	$104.38	7.598%	$112.3108	$112.31	$112.30	$112.30
7 purchase totals =	$791.45		$852.3300	$852.33	$852.30	$852.20