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	$178.88	6.674%	$190.8185	$190.82	$190.80	$190.80
Purchase #2	$146.65	6.851%	$156.697	$156.70	$156.70	$156.70
Purchase #3	$126.54	3.794%	$131.3409	$131.34	$131.35	$131.30
Purchase #4	$140.96	10.423%	$155.6523	$155.65	$155.65	$155.70
Purchase #5	$42.59	7.548%	$45.8047	$45.80	$45.80	$45.80
Purchase #6	$22.45	10.218%	$24.7439	$24.74	$24.75	$24.70
Purchase #7	$245.56	12.383%	$275.9677	$275.97	$275.95	$276.00
7 purchase totals =	$903.63		$981.0250	$981.02	$981.00	$981.00