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	$131.55	9.353%	$143.8539	$143.85	$143.85	$143.90
Purchase #2	$61.80	4.381%	$64.5075	$64.51	$64.50	$64.50
Purchase #3	$20.56	7.443%	$22.0903	$22.09	$22.10	$22.10
Purchase #4	$167.93	10.396%	$185.388	$185.39	$185.40	$185.40
Purchase #5	$128.78	8.743%	$140.0392	$140.04	$140.05	$140.00
Purchase #6	$236.33	5.141%	$248.4797	$248.48	$248.50	$248.50
Purchase #7	$24.71	12.394%	$27.7726	$27.77	$27.75	$27.80
7 purchase totals =	$771.66		$832.1312	$832.13	$832.15	$832.20