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	$222.54	9.497%	$243.6746	$243.67	$243.65	$243.70
Purchase #2	$242.28	11.757%	$270.7649	$270.76	$270.75	$270.80
Purchase #3	$201.29	12.342%	$226.1332	$226.13	$226.15	$226.10
Purchase #4	$196.34	9.815%	$215.6108	$215.61	$215.60	$215.60
Purchase #5	$81.72	9.412%	$89.4115	$89.41	$89.40	$89.40
Purchase #6	$7.72	10.715%	$8.5472	$8.55	$8.55	$8.50
Purchase #7	$60.59	11.243%	$67.4021	$67.40	$67.40	$67.40
7 purchase totals =	$1,012.48		$1,121.5443	$1,121.53	$1,121.50	$1,121.50