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	$89.46	12.617%	$100.7472	$100.75	$100.75	$100.70
Purchase #2	$32.89	8.373%	$35.6439	$35.64	$35.65	$35.60
Purchase #3	$99.85	12.107%	$111.9388	$111.94	$111.95	$111.90
Purchase #4	$38.76	11.549%	$43.2364	$43.24	$43.25	$43.20
Purchase #5	$233.60	7.134%	$250.265	$250.27	$250.25	$250.30
Purchase #6	$178.95	8.259%	$193.7295	$193.73	$193.75	$193.70
Purchase #7	$223.86	12.661%	$252.2029	$252.20	$252.20	$252.20
7 purchase totals =	$897.37		$987.7637	$987.77	$987.80	$987.60