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	$68.60	11.178%	$76.2681	$76.27	$76.25	$76.30
Purchase #2	$140.46	8.846%	$152.8851	$152.89	$152.90	$152.90
Purchase #3	$159.58	7.642%	$171.7751	$171.78	$171.80	$171.80
Purchase #4	$114.26	12.663%	$128.7287	$128.73	$128.75	$128.70
Purchase #5	$130.25	5.620%	$137.5701	$137.57	$137.55	$137.60
Purchase #6	$146.44	10.656%	$162.0446	$162.04	$162.05	$162.00
Purchase #7	$35.80	5.689%	$37.8367	$37.84	$37.85	$37.80
7 purchase totals =	$795.39		$867.1084	$867.12	$867.15	$867.10