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	$8.29	5.132%	$8.7154	$8.72	$8.70	$8.70
Purchase #2	$202.61	13.285%	$229.5267	$229.53	$229.55	$229.50
Purchase #3	$64.71	12.143%	$72.5677	$72.57	$72.55	$72.60
Purchase #4	$248.70	11.809%	$278.069	$278.07	$278.05	$278.10
Purchase #5	$91.67	12.237%	$102.8877	$102.89	$102.90	$102.90
Purchase #6	$170.30	9.461%	$186.4121	$186.41	$186.40	$186.40
Purchase #7	$161.89	6.490%	$172.3967	$172.40	$172.40	$172.40
7 purchase totals =	$948.17		$1,050.5753	$1,050.59	$1,050.55	$1,050.60