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	$38.85	5.605%	$41.0275	$41.03	$41.05	$41.00
Purchase #2	$105.55	10.446%	$116.5758	$116.58	$116.60	$116.60
Purchase #3	$166.42	12.656%	$187.4821	$187.48	$187.50	$187.50
Purchase #4	$155.42	6.482%	$165.4943	$165.49	$165.50	$165.50
Purchase #5	$239.90	4.509%	$250.7171	$250.72	$250.70	$250.70
Purchase #6	$6.81	5.436%	$7.1802	$7.18	$7.20	$7.20
Purchase #7	$235.52	7.440%	$253.0427	$253.04	$253.05	$253.00
7 purchase totals =	$948.47		$1,021.5197	$1,021.52	$1,021.60	$1,021.50