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	$217.30	7.337%	$233.2433	$233.24	$233.25	$233.20
Purchase #2	$237.47	13.655%	$269.8965	$269.90	$269.90	$269.90
Purchase #3	$103.79	8.457%	$112.5675	$112.57	$112.55	$112.60
Purchase #4	$18.77	12.470%	$21.1106	$21.11	$21.10	$21.10
Purchase #5	$109.41	8.666%	$118.8915	$118.89	$118.90	$118.90
Purchase #6	$82.65	13.707%	$93.9788	$93.98	$94.00	$94.00
Purchase #7	$90.86	4.742%	$95.1686	$95.17	$95.15	$95.20
7 purchase totals =	$860.25		$944.8568	$944.86	$944.85	$944.90