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	$57.97	5.422%	$61.1131	$61.11	$61.10	$61.10
Purchase #2	$35.38	8.800%	$38.4934	$38.49	$38.50	$38.50
Purchase #3	$33.45	9.217%	$36.5331	$36.53	$36.55	$36.50
Purchase #4	$102.27	11.396%	$113.9247	$113.92	$113.90	$113.90
Purchase #5	$153.86	11.333%	$171.297	$171.30	$171.30	$171.30
Purchase #6	$58.80	7.228%	$63.0501	$63.05	$63.05	$63.10
Purchase #7	$130.39	10.530%	$144.1201	$144.12	$144.10	$144.10
7 purchase totals =	$572.12		$628.5315	$628.52	$628.50	$628.50