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	$193.67	3.383%	$200.2219	$200.22	$200.20	$200.20
Purchase #2	$105.94	5.188%	$111.4362	$111.44	$111.45	$111.40
Purchase #3	$163.85	13.842%	$186.5301	$186.53	$186.55	$186.50
Purchase #4	$159.50	7.158%	$170.917	$170.92	$170.90	$170.90
Purchase #5	$115.26	7.217%	$123.5783	$123.58	$123.60	$123.60
Purchase #6	$246.29	3.727%	$255.4692	$255.47	$255.45	$255.50
Purchase #7	$20.38	9.588%	$22.334	$22.33	$22.35	$22.30
7 purchase totals =	$1,004.89		$1,070.4867	$1,070.49	$1,070.50	$1,070.40