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	$113.54	11.664%	$126.7833	$126.78	$126.80	$126.80
Purchase #2	$36.54	12.397%	$41.0699	$41.07	$41.05	$41.10
Purchase #3	$198.58	5.846%	$210.189	$210.19	$210.20	$210.20
Purchase #4	$9.71	10.258%	$10.7061	$10.71	$10.70	$10.70
Purchase #5	$72.92	8.221%	$78.9148	$78.91	$78.90	$78.90
Purchase #6	$184.51	6.565%	$196.6231	$196.62	$196.60	$196.60
Purchase #7	$236.92	11.503%	$264.1729	$264.17	$264.15	$264.20
7 purchase totals =	$852.72		$928.4591	$928.45	$928.40	$928.50