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	$145.46	3.618%	$150.7227	$150.72	$150.70	$150.70
Purchase #2	$195.82	12.695%	$220.6793	$220.68	$220.70	$220.70
Purchase #3	$183.54	4.531%	$191.8562	$191.86	$191.85	$191.90
Purchase #4	$198.84	5.486%	$209.7484	$209.75	$209.75	$209.70
Purchase #5	$20.86	5.252%	$21.9556	$21.96	$21.95	$22.00
Purchase #6	$80.38	13.166%	$90.9628	$90.96	$90.95	$91.00
Purchase #7	$177.97	12.819%	$200.784	$200.78	$200.80	$200.80
7 purchase totals =	$1,002.87		$1,086.7090	$1,086.71	$1,086.70	$1,086.80