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	$99.26	4.278%	$103.5063	$103.51	$103.50	$103.50
Purchase #2	$112.65	12.416%	$126.6366	$126.64	$126.65	$126.60
Purchase #3	$226.37	13.474%	$256.8711	$256.87	$256.85	$256.90
Purchase #4	$61.54	3.238%	$63.5327	$63.53	$63.55	$63.50
Purchase #5	$29.34	10.460%	$32.409	$32.41	$32.40	$32.40
Purchase #6	$101.39	10.132%	$111.6628	$111.66	$111.65	$111.70
Purchase #7	$167.33	7.366%	$179.6555	$179.66	$179.65	$179.70
7 purchase totals =	$797.88		$874.2740	$874.28	$874.25	$874.30