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	$120.57	5.199%	$126.8384	$126.84	$126.85	$126.80
Purchase #2	$150.29	5.432%	$158.4538	$158.45	$158.45	$158.50
Purchase #3	$168.80	11.650%	$188.4652	$188.47	$188.45	$188.50
Purchase #4	$137.31	3.790%	$142.514	$142.51	$142.50	$142.50
Purchase #5	$84.59	12.339%	$95.0276	$95.03	$95.05	$95.00
Purchase #6	$45.73	6.770%	$48.8259	$48.83	$48.85	$48.80
Purchase #7	$242.74	10.651%	$268.5942	$268.59	$268.60	$268.60
7 purchase totals =	$950.03		$1,028.7191	$1,028.72	$1,028.75	$1,028.70