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	$92.49	3.530%	$95.7549	$95.75	$95.75	$95.80
Purchase #2	$179.82	10.281%	$198.3073	$198.31	$198.30	$198.30
Purchase #3	$88.39	8.410%	$95.8236	$95.82	$95.80	$95.80
Purchase #4	$102.47	6.790%	$109.4277	$109.43	$109.45	$109.40
Purchase #5	$121.83	12.778%	$137.3974	$137.40	$137.40	$137.40
Purchase #6	$76.72	12.800%	$86.5402	$86.54	$86.55	$86.50
Purchase #7	$30.36	6.468%	$32.3237	$32.32	$32.30	$32.30
7 purchase totals =	$692.08		$755.5748	$755.57	$755.55	$755.50