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	$237.83	12.786%	$268.2389	$268.24	$268.25	$268.20
Purchase #2	$56.54	9.261%	$61.7762	$61.78	$61.80	$61.80
Purchase #3	$217.87	9.630%	$238.8509	$238.85	$238.85	$238.90
Purchase #4	$216.28	7.684%	$232.899	$232.90	$232.90	$232.90
Purchase #5	$142.72	8.755%	$155.2151	$155.22	$155.20	$155.20
Purchase #6	$175.91	11.600%	$196.3156	$196.32	$196.30	$196.30
Purchase #7	$237.71	7.580%	$255.7284	$255.73	$255.75	$255.70
7 purchase totals =	$1,284.86		$1,409.0241	$1,409.04	$1,409.05	$1,409.00