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	$68.39	11.485%	$76.2446	$76.24	$76.25	$76.20
Purchase #2	$33.39	6.583%	$35.5881	$35.59	$35.60	$35.60
Purchase #3	$131.71	8.254%	$142.5813	$142.58	$142.60	$142.60
Purchase #4	$147.75	7.133%	$158.289	$158.29	$158.30	$158.30
Purchase #5	$67.75	4.869%	$71.0487	$71.05	$71.05	$71.00
Purchase #6	$190.93	11.339%	$212.5796	$212.58	$212.60	$212.60
Purchase #7	$213.64	7.121%	$228.8533	$228.85	$228.85	$228.90
7 purchase totals =	$853.56		$925.1846	$925.18	$925.25	$925.20