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	$144.74	6.703%	$154.4419	$154.44	$154.45	$154.40
Purchase #2	$69.56	3.807%	$72.2081	$72.21	$72.20	$72.20
Purchase #3	$216.35	13.592%	$245.7563	$245.76	$245.75	$245.80
Purchase #4	$59.32	6.626%	$63.2505	$63.25	$63.25	$63.30
Purchase #5	$61.96	7.423%	$66.5593	$66.56	$66.55	$66.60
Purchase #6	$30.41	6.469%	$32.3772	$32.38	$32.40	$32.40
Purchase #7	$222.55	12.152%	$249.5943	$249.59	$249.60	$249.60
7 purchase totals =	$804.89		$884.1876	$884.19	$884.20	$884.30