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	$94.73	6.794%	$101.166	$101.17	$101.15	$101.20
Purchase #2	$73.94	13.411%	$83.8561	$83.86	$83.85	$83.90
Purchase #3	$11.86	3.211%	$12.2408	$12.24	$12.25	$12.20
Purchase #4	$182.29	6.649%	$194.4105	$194.41	$194.40	$194.40
Purchase #5	$244.59	11.420%	$272.5222	$272.52	$272.50	$272.50
Purchase #6	$127.45	9.502%	$139.5603	$139.56	$139.55	$139.60
Purchase #7	$160.63	11.609%	$179.2775	$179.28	$179.30	$179.30
7 purchase totals =	$895.49		$983.0334	$983.04	$983.00	$983.10