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	$179.64	3.344%	$185.6472	$185.65	$185.65	$185.60
Purchase #2	$99.46	4.744%	$104.1784	$104.18	$104.20	$104.20
Purchase #3	$110.62	11.171%	$122.9774	$122.98	$123.00	$123.00
Purchase #4	$186.26	7.719%	$200.6374	$200.64	$200.65	$200.60
Purchase #5	$127.59	10.119%	$140.5008	$140.50	$140.50	$140.50
Purchase #6	$58.53	5.210%	$61.5794	$61.58	$61.60	$61.60
Purchase #7	$99.89	13.518%	$113.3931	$113.39	$113.40	$113.40
7 purchase totals =	$861.99		$928.9137	$928.92	$929.00	$928.90