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	$56.87	12.645%	$64.0612	$64.06	$64.05	$64.10
Purchase #2	$66.45	9.711%	$72.903	$72.90	$72.90	$72.90
Purchase #3	$37.29	9.390%	$40.7915	$40.79	$40.80	$40.80
Purchase #4	$45.90	3.301%	$47.4152	$47.42	$47.40	$47.40
Purchase #5	$210.55	11.141%	$234.0074	$234.01	$234.00	$234.00
Purchase #6	$114.83	11.394%	$127.9137	$127.91	$127.90	$127.90
Purchase #7	$91.50	12.124%	$102.5935	$102.59	$102.60	$102.60
7 purchase totals =	$623.39		$689.6855	$689.68	$689.65	$689.70