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	$128.41	13.176%	$145.3293	$145.33	$145.35	$145.30
Purchase #2	$162.44	3.508%	$168.1384	$168.14	$168.15	$168.10
Purchase #3	$61.53	9.431%	$67.3329	$67.33	$67.35	$67.30
Purchase #4	$191.59	4.285%	$199.7996	$199.80	$199.80	$199.80
Purchase #5	$6.81	8.379%	$7.3806	$7.38	$7.40	$7.40
Purchase #6	$91.66	13.213%	$103.771	$103.77	$103.75	$103.80
Purchase #7	$89.45	8.723%	$97.2527	$97.25	$97.25	$97.30
7 purchase totals =	$731.89		$789.0045	$789.00	$789.05	$789.00