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	$56.42	13.190%	$63.8618	$63.86	$63.85	$63.90
Purchase #2	$80.54	12.342%	$90.4802	$90.48	$90.50	$90.50
Purchase #3	$126.48	3.483%	$130.8853	$130.89	$130.90	$130.90
Purchase #4	$57.56	12.222%	$64.595	$64.60	$64.60	$64.60
Purchase #5	$61.47	11.504%	$68.5415	$68.54	$68.55	$68.50
Purchase #6	$25.39	11.374%	$28.2779	$28.28	$28.30	$28.30
Purchase #7	$80.69	6.784%	$86.164	$86.16	$86.15	$86.20
7 purchase totals =	$488.55		$532.8057	$532.81	$532.85	$532.90