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	$44.38	6.459%	$47.2465	$47.25	$47.25	$47.20
Purchase #2	$179.93	5.266%	$189.4051	$189.41	$189.40	$189.40
Purchase #3	$213.38	5.480%	$225.0732	$225.07	$225.05	$225.10
Purchase #4	$227.95	12.572%	$256.6079	$256.61	$256.60	$256.60
Purchase #5	$85.28	4.370%	$89.0067	$89.01	$89.00	$89.00
Purchase #6	$76.26	4.605%	$79.7718	$79.77	$79.75	$79.80
Purchase #7	$76.82	6.816%	$82.0561	$82.06	$82.05	$82.10
7 purchase totals =	$904.00		$969.1673	$969.18	$969.10	$969.20