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	$199.42	11.631%	$222.6145	$222.61	$222.60	$222.60
Purchase #2	$102.39	8.426%	$111.0174	$111.02	$111.00	$111.00
Purchase #3	$77.80	11.706%	$86.9073	$86.91	$86.90	$86.90
Purchase #4	$19.94	10.644%	$22.0624	$22.06	$22.05	$22.10
Purchase #5	$61.37	9.787%	$67.3763	$67.38	$67.40	$67.40
Purchase #6	$244.47	7.281%	$262.2699	$262.27	$262.25	$262.30
Purchase #7	$174.60	8.459%	$189.3694	$189.37	$189.35	$189.40
7 purchase totals =	$879.99		$961.6172	$961.62	$961.55	$961.70