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	$228.73	9.673%	$250.8551	$250.86	$250.85	$250.90
Purchase #2	$139.82	13.390%	$158.5419	$158.54	$158.55	$158.50
Purchase #3	$208.29	9.722%	$228.54	$228.54	$228.55	$228.50
Purchase #4	$89.51	11.132%	$99.4743	$99.47	$99.45	$99.50
Purchase #5	$124.38	12.639%	$140.1004	$140.10	$140.10	$140.10
Purchase #6	$85.59	3.845%	$88.8809	$88.88	$88.90	$88.90
Purchase #7	$217.54	10.663%	$240.7363	$240.74	$240.75	$240.70
7 purchase totals =	$1,093.86		$1,207.1289	$1,207.13	$1,207.15	$1,207.10