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	$131.52	6.151%	$139.6098	$139.61	$139.60	$139.60
Purchase #2	$89.54	10.175%	$98.6507	$98.65	$98.65	$98.70
Purchase #3	$234.30	12.831%	$264.363	$264.36	$264.35	$264.40
Purchase #4	$228.96	12.165%	$256.813	$256.81	$256.80	$256.80
Purchase #5	$81.32	13.604%	$92.3828	$92.38	$92.40	$92.40
Purchase #6	$67.49	7.424%	$72.5005	$72.50	$72.50	$72.50
Purchase #7	$199.40	5.110%	$209.5893	$209.59	$209.60	$209.60
7 purchase totals =	$1,032.53		$1,133.9091	$1,133.90	$1,133.90	$1,134.00