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	$188.37	12.570%	$212.0481	$212.05	$212.05	$212.00
Purchase #2	$153.77	7.381%	$165.1198	$165.12	$165.10	$165.10
Purchase #3	$167.92	11.662%	$187.5028	$187.50	$187.50	$187.50
Purchase #4	$53.26	11.759%	$59.5228	$59.52	$59.50	$59.50
Purchase #5	$135.41	4.757%	$141.8515	$141.85	$141.85	$141.90
Purchase #6	$132.71	9.176%	$144.8875	$144.89	$144.90	$144.90
Purchase #7	$143.73	7.440%	$154.4235	$154.42	$154.40	$154.40
7 purchase totals =	$975.17		$1,065.3560	$1,065.35	$1,065.30	$1,065.30