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	$128.54	6.636%	$137.0699	$137.07	$137.05	$137.10
Purchase #2	$122.63	3.130%	$126.4683	$126.47	$126.45	$126.50
Purchase #3	$150.37	8.232%	$162.7485	$162.75	$162.75	$162.70
Purchase #4	$137.33	9.506%	$150.3846	$150.38	$150.40	$150.40
Purchase #5	$238.69	7.460%	$256.4963	$256.50	$256.50	$256.50
Purchase #6	$80.69	6.774%	$86.1559	$86.16	$86.15	$86.20
Purchase #7	$207.29	10.405%	$228.8585	$228.86	$228.85	$228.90
7 purchase totals =	$1,065.54		$1,148.1820	$1,148.19	$1,148.15	$1,148.30