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	$137.72	7.693%	$148.3148	$148.31	$148.30	$148.30
Purchase #2	$218.70	6.802%	$233.576	$233.58	$233.60	$233.60
Purchase #3	$86.47	5.626%	$91.3348	$91.33	$91.35	$91.30
Purchase #4	$54.65	8.794%	$59.4559	$59.46	$59.45	$59.50
Purchase #5	$248.92	5.526%	$262.6753	$262.68	$262.70	$262.70
Purchase #6	$110.65	7.722%	$119.1944	$119.19	$119.20	$119.20
Purchase #7	$121.51	7.302%	$130.3827	$130.38	$130.40	$130.40
7 purchase totals =	$978.62		$1,044.9339	$1,044.93	$1,045.00	$1,045.00