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	$216.29	11.351%	$240.8411	$240.84	$240.85	$240.80
Purchase #2	$162.41	5.715%	$171.6917	$171.69	$171.70	$171.70
Purchase #3	$111.54	6.489%	$118.7778	$118.78	$118.80	$118.80
Purchase #4	$248.52	13.430%	$281.8962	$281.90	$281.90	$281.90
Purchase #5	$242.35	3.315%	$250.3839	$250.38	$250.40	$250.40
Purchase #6	$179.53	6.464%	$191.1348	$191.13	$191.15	$191.10
Purchase #7	$223.59	4.649%	$233.9847	$233.98	$234.00	$234.00
7 purchase totals =	$1,384.23		$1,488.7102	$1,488.70	$1,488.80	$1,488.70