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	$233.29	10.868%	$258.644	$258.64	$258.65	$258.60
Purchase #2	$56.28	5.511%	$59.3816	$59.38	$59.40	$59.40
Purchase #3	$229.25	5.322%	$241.4507	$241.45	$241.45	$241.50
Purchase #4	$100.52	10.419%	$110.9932	$110.99	$111.00	$111.00
Purchase #5	$165.47	12.669%	$186.4334	$186.43	$186.45	$186.40
Purchase #6	$31.85	4.257%	$33.2059	$33.21	$33.20	$33.20
Purchase #7	$194.88	13.136%	$220.4794	$220.48	$220.50	$220.50
7 purchase totals =	$1,011.54		$1,110.5882	$1,110.58	$1,110.65	$1,110.60