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	$198.76	3.656%	$206.0267	$206.03	$206.05	$206.00
Purchase #2	$162.93	5.833%	$172.4337	$172.43	$172.45	$172.40
Purchase #3	$82.37	11.199%	$91.5946	$91.59	$91.60	$91.60
Purchase #4	$102.80	5.843%	$108.8066	$108.81	$108.80	$108.80
Purchase #5	$9.61	13.569%	$10.914	$10.91	$10.90	$10.90
Purchase #6	$221.69	4.306%	$231.236	$231.24	$231.25	$231.20
Purchase #7	$221.60	3.728%	$229.8612	$229.86	$229.85	$229.90
7 purchase totals =	$999.76		$1,050.8728	$1,050.87	$1,050.90	$1,050.80