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	$239.50	9.844%	$263.0764	$263.08	$263.10	$263.10
Purchase #2	$34.85	6.489%	$37.1114	$37.11	$37.10	$37.10
Purchase #3	$238.53	11.258%	$265.3837	$265.38	$265.40	$265.40
Purchase #4	$172.37	9.624%	$188.9589	$188.96	$188.95	$189.00
Purchase #5	$169.37	9.411%	$185.3094	$185.31	$185.30	$185.30
Purchase #6	$85.81	9.495%	$93.9577	$93.96	$93.95	$94.00
Purchase #7	$215.64	3.182%	$222.5017	$222.50	$222.50	$222.50
7 purchase totals =	$1,156.07		$1,256.2992	$1,256.30	$1,256.30	$1,256.40