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	$210.26	8.520%	$228.1742	$228.17	$228.15	$228.20
Purchase #2	$219.36	12.839%	$247.5236	$247.52	$247.50	$247.50
Purchase #3	$27.59	4.861%	$28.9311	$28.93	$28.95	$28.90
Purchase #4	$94.53	4.116%	$98.4209	$98.42	$98.40	$98.40
Purchase #5	$131.55	7.776%	$141.7793	$141.78	$141.80	$141.80
Purchase #6	$18.81	7.638%	$20.2467	$20.25	$20.25	$20.20
Purchase #7	$221.31	11.734%	$247.2785	$247.28	$247.30	$247.30
7 purchase totals =	$923.41		$1,012.3543	$1,012.35	$1,012.35	$1,012.30