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	$82.43	9.846%	$90.5461	$90.55	$90.55	$90.50
Purchase #2	$56.34	13.344%	$63.858	$63.86	$63.85	$63.90
Purchase #3	$103.68	3.315%	$107.117	$107.12	$107.10	$107.10
Purchase #4	$193.76	8.817%	$210.8438	$210.84	$210.85	$210.80
Purchase #5	$195.48	13.214%	$221.3107	$221.31	$221.30	$221.30
Purchase #6	$12.36	12.340%	$13.8852	$13.89	$13.90	$13.90
Purchase #7	$144.42	6.199%	$153.3726	$153.37	$153.35	$153.40
7 purchase totals =	$788.47		$860.9334	$860.94	$860.90	$860.90