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	$192.58	10.548%	$212.8933	$212.89	$212.90	$212.90
Purchase #2	$98.95	11.782%	$110.6083	$110.61	$110.60	$110.60
Purchase #3	$99.47	3.443%	$102.8948	$102.89	$102.90	$102.90
Purchase #4	$156.66	10.381%	$172.9229	$172.92	$172.90	$172.90
Purchase #5	$242.36	12.800%	$273.3821	$273.38	$273.40	$273.40
Purchase #6	$5.56	4.713%	$5.822	$5.82	$5.80	$5.80
Purchase #7	$48.52	11.840%	$54.2648	$54.26	$54.25	$54.30
7 purchase totals =	$844.10		$932.7882	$932.77	$932.75	$932.80