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	$90.59	11.238%	$100.7705	$100.77	$100.75	$100.80
Purchase #2	$19.74	10.769%	$21.8658	$21.87	$21.85	$21.90
Purchase #3	$192.47	5.514%	$203.0828	$203.08	$203.10	$203.10
Purchase #4	$64.53	11.419%	$71.8987	$71.90	$71.90	$71.90
Purchase #5	$162.85	11.657%	$181.8334	$181.83	$181.85	$181.80
Purchase #6	$99.79	12.865%	$112.628	$112.63	$112.65	$112.60
Purchase #7	$88.25	12.726%	$99.4807	$99.48	$99.50	$99.50
7 purchase totals =	$718.22		$791.5599	$791.56	$791.60	$791.60