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	$198.30	10.671%	$219.4606	$219.46	$219.45	$219.50
Purchase #2	$99.85	3.522%	$103.3667	$103.37	$103.35	$103.40
Purchase #3	$169.59	11.863%	$189.7085	$189.71	$189.70	$189.70
Purchase #4	$148.35	7.780%	$159.8916	$159.89	$159.90	$159.90
Purchase #5	$192.68	13.609%	$218.9018	$218.90	$218.90	$218.90
Purchase #6	$68.69	3.526%	$71.112	$71.11	$71.10	$71.10
Purchase #7	$38.96	5.180%	$40.9781	$40.98	$41.00	$41.00
7 purchase totals =	$916.42		$1,003.4193	$1,003.42	$1,003.40	$1,003.50