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	$109.39	3.537%	$113.2591	$113.26	$113.25	$113.30
Purchase #2	$141.91	6.253%	$150.7836	$150.78	$150.80	$150.80
Purchase #3	$20.42	7.107%	$21.8712	$21.87	$21.85	$21.90
Purchase #4	$179.32	11.864%	$200.5945	$200.59	$200.60	$200.60
Purchase #5	$111.74	12.782%	$126.0226	$126.02	$126.00	$126.00
Purchase #6	$25.80	12.465%	$29.016	$29.02	$29.00	$29.00
Purchase #7	$174.61	10.572%	$193.0698	$193.07	$193.05	$193.10
7 purchase totals =	$763.19		$834.6168	$834.61	$834.55	$834.70