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	$119.85	3.219%	$123.708	$123.71	$123.70	$123.70
Purchase #2	$96.75	11.508%	$107.884	$107.88	$107.90	$107.90
Purchase #3	$45.54	5.825%	$48.1927	$48.19	$48.20	$48.20
Purchase #4	$33.47	8.754%	$36.4	$36.40	$36.40	$36.40
Purchase #5	$196.59	9.762%	$215.7811	$215.78	$215.80	$215.80
Purchase #6	$78.87	13.503%	$89.5198	$89.52	$89.50	$89.50
Purchase #7	$52.32	9.340%	$57.2067	$57.21	$57.20	$57.20
7 purchase totals =	$623.39		$678.6923	$678.69	$678.70	$678.70