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	$100.60	11.689%	$112.3591	$112.36	$112.35	$112.40
Purchase #2	$75.85	6.222%	$80.5694	$80.57	$80.55	$80.60
Purchase #3	$89.69	9.219%	$97.9585	$97.96	$97.95	$98.00
Purchase #4	$212.90	7.834%	$229.5786	$229.58	$229.60	$229.60
Purchase #5	$222.61	3.124%	$229.5643	$229.56	$229.55	$229.60
Purchase #6	$62.67	7.675%	$67.4799	$67.48	$67.50	$67.50
Purchase #7	$231.30	7.152%	$247.8426	$247.84	$247.85	$247.80
7 purchase totals =	$995.62		$1,065.3524	$1,065.35	$1,065.35	$1,065.50