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	$107.54	10.232%	$118.5435	$118.54	$118.55	$118.50
Purchase #2	$141.55	3.607%	$146.6557	$146.66	$146.65	$146.70
Purchase #3	$109.93	12.687%	$123.8768	$123.88	$123.90	$123.90
Purchase #4	$135.53	5.451%	$142.9177	$142.92	$142.90	$142.90
Purchase #5	$209.46	6.470%	$223.0121	$223.01	$223.00	$223.00
Purchase #6	$99.25	12.172%	$111.3307	$111.33	$111.35	$111.30
Purchase #7	$88.26	13.559%	$100.2272	$100.23	$100.25	$100.20
7 purchase totals =	$891.52		$966.5637	$966.57	$966.60	$966.50