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	$209.64	3.278%	$216.512	$216.51	$216.50	$216.50
Purchase #2	$76.53	12.261%	$85.9133	$85.91	$85.90	$85.90
Purchase #3	$40.70	12.641%	$45.8449	$45.84	$45.85	$45.80
Purchase #4	$128.36	10.270%	$141.5426	$141.54	$141.55	$141.50
Purchase #5	$18.86	10.504%	$20.8411	$20.84	$20.85	$20.80
Purchase #6	$136.63	4.457%	$142.7196	$142.72	$142.70	$142.70
Purchase #7	$100.52	3.576%	$104.1146	$104.11	$104.10	$104.10
7 purchase totals =	$711.24		$757.4881	$757.47	$757.45	$757.30