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	$57.51	11.223%	$63.9643	$63.96	$63.95	$64.00
Purchase #2	$59.86	13.271%	$67.804	$67.80	$67.80	$67.80
Purchase #3	$127.44	7.140%	$136.5392	$136.54	$136.55	$136.50
Purchase #4	$34.85	10.700%	$38.579	$38.58	$38.60	$38.60
Purchase #5	$98.71	9.831%	$108.4142	$108.41	$108.40	$108.40
Purchase #6	$237.46	11.144%	$263.9225	$263.92	$263.90	$263.90
Purchase #7	$110.37	12.666%	$124.3495	$124.35	$124.35	$124.30
7 purchase totals =	$726.20		$803.5727	$803.56	$803.55	$803.50