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	$192.78	5.645%	$203.6624	$203.66	$203.65	$203.70
Purchase #2	$193.59	6.256%	$205.701	$205.70	$205.70	$205.70
Purchase #3	$188.70	4.133%	$196.499	$196.50	$196.50	$196.50
Purchase #4	$155.78	8.870%	$169.5977	$169.60	$169.60	$169.60
Purchase #5	$17.25	6.836%	$18.4292	$18.43	$18.45	$18.40
Purchase #6	$91.29	12.626%	$102.8163	$102.82	$102.80	$102.80
Purchase #7	$249.92	7.824%	$269.4737	$269.47	$269.45	$269.50
7 purchase totals =	$1,089.31		$1,166.1793	$1,166.18	$1,166.15	$1,166.20