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	$196.73	11.737%	$219.8202	$219.82	$219.80	$219.80
Purchase #2	$129.89	12.799%	$146.5146	$146.51	$146.50	$146.50
Purchase #3	$56.52	12.269%	$63.4544	$63.45	$63.45	$63.50
Purchase #4	$41.49	3.328%	$42.8708	$42.87	$42.85	$42.90
Purchase #5	$83.29	7.327%	$89.3927	$89.39	$89.40	$89.40
Purchase #6	$212.42	4.518%	$222.0171	$222.02	$222.00	$222.00
Purchase #7	$154.59	6.461%	$164.5781	$164.58	$164.60	$164.60
7 purchase totals =	$874.93		$948.6479	$948.64	$948.60	$948.70