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	$77.45	10.595%	$85.6558	$85.66	$85.65	$85.70
Purchase #2	$28.88	11.629%	$32.2385	$32.24	$32.25	$32.20
Purchase #3	$116.98	12.781%	$131.9312	$131.93	$131.95	$131.90
Purchase #4	$112.47	7.172%	$120.5363	$120.54	$120.55	$120.50
Purchase #5	$114.46	13.682%	$130.1204	$130.12	$130.10	$130.10
Purchase #6	$58.35	7.545%	$62.7525	$62.75	$62.75	$62.80
Purchase #7	$109.41	13.846%	$124.5589	$124.56	$124.55	$124.60
7 purchase totals =	$618.00		$687.7936	$687.80	$687.80	$687.80