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	$116.49	9.521%	$127.581	$127.58	$127.60	$127.60
Purchase #2	$98.55	9.192%	$107.6087	$107.61	$107.60	$107.60
Purchase #3	$50.52	12.372%	$56.7703	$56.77	$56.75	$56.80
Purchase #4	$113.86	12.131%	$127.6724	$127.67	$127.65	$127.70
Purchase #5	$61.62	11.496%	$68.7038	$68.70	$68.70	$68.70
Purchase #6	$167.74	11.834%	$187.5904	$187.59	$187.60	$187.60
Purchase #7	$68.60	3.619%	$71.0826	$71.08	$71.10	$71.10
7 purchase totals =	$677.38		$747.0092	$747.00	$747.00	$747.10