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	$66.66	7.811%	$71.8668	$71.87	$71.85	$71.90
Purchase #2	$182.96	9.496%	$200.3339	$200.33	$200.35	$200.30
Purchase #3	$205.33	3.652%	$212.8287	$212.83	$212.85	$212.80
Purchase #4	$65.86	12.148%	$73.8607	$73.86	$73.85	$73.90
Purchase #5	$119.32	5.169%	$125.4877	$125.49	$125.50	$125.50
Purchase #6	$125.37	3.838%	$130.1817	$130.18	$130.20	$130.20
Purchase #7	$113.48	12.448%	$127.606	$127.61	$127.60	$127.60
7 purchase totals =	$878.98		$942.1655	$942.17	$942.20	$942.20