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	$30.31	7.353%	$32.5387	$32.54	$32.55	$32.50
Purchase #2	$81.29	12.136%	$91.1554	$91.16	$91.15	$91.20
Purchase #3	$25.97	12.137%	$29.122	$29.12	$29.10	$29.10
Purchase #4	$116.88	5.678%	$123.5164	$123.52	$123.50	$123.50
Purchase #5	$125.36	4.532%	$131.0413	$131.04	$131.05	$131.00
Purchase #6	$169.51	7.640%	$182.4606	$182.46	$182.45	$182.50
Purchase #7	$164.29	6.106%	$174.3215	$174.32	$174.30	$174.30
7 purchase totals =	$713.61		$764.1559	$764.16	$764.10	$764.10