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	$175.66	11.295%	$195.5008	$195.50	$195.50	$195.50
Purchase #2	$131.39	10.656%	$145.3909	$145.39	$145.40	$145.40
Purchase #3	$30.41	6.431%	$32.3657	$32.37	$32.35	$32.40
Purchase #4	$121.77	12.613%	$137.1289	$137.13	$137.15	$137.10
Purchase #5	$13.79	11.130%	$15.3248	$15.32	$15.30	$15.30
Purchase #6	$131.74	12.226%	$147.8465	$147.85	$147.85	$147.80
Purchase #7	$100.89	3.550%	$104.4716	$104.47	$104.45	$104.50
7 purchase totals =	$705.65		$778.0292	$778.03	$778.00	$778.00