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	$143.74	6.339%	$152.8517	$152.85	$152.85	$152.90
Purchase #2	$152.99	13.696%	$173.9435	$173.94	$173.95	$173.90
Purchase #3	$30.44	4.660%	$31.8585	$31.86	$31.85	$31.90
Purchase #4	$98.55	7.608%	$106.0477	$106.05	$106.05	$106.00
Purchase #5	$68.96	5.314%	$72.6245	$72.62	$72.60	$72.60
Purchase #6	$237.83	13.828%	$270.7171	$270.72	$270.70	$270.70
Purchase #7	$248.60	4.140%	$258.892	$258.89	$258.90	$258.90
7 purchase totals =	$981.11		$1,066.9350	$1,066.93	$1,066.90	$1,066.90