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	$209.74	4.216%	$218.5826	$218.58	$218.60	$218.60
Purchase #2	$78.66	4.603%	$82.2807	$82.28	$82.30	$82.30
Purchase #3	$179.67	8.844%	$195.56	$195.56	$195.55	$195.60
Purchase #4	$140.36	7.158%	$150.407	$150.41	$150.40	$150.40
Purchase #5	$65.40	11.638%	$73.0113	$73.01	$73.00	$73.00
Purchase #6	$29.83	11.594%	$33.2885	$33.29	$33.30	$33.30
Purchase #7	$136.35	6.285%	$144.9196	$144.92	$144.90	$144.90
7 purchase totals =	$840.01		$898.0497	$898.05	$898.05	$898.10