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	$209.81	11.508%	$233.9549	$233.95	$233.95	$234.00
Purchase #2	$100.72	5.150%	$105.9071	$105.91	$105.90	$105.90
Purchase #3	$59.98	3.868%	$62.3	$62.30	$62.30	$62.30
Purchase #4	$24.94	12.566%	$28.074	$28.07	$28.05	$28.10
Purchase #5	$110.27	3.175%	$113.7711	$113.77	$113.75	$113.80
Purchase #6	$151.72	5.547%	$160.1359	$160.14	$160.15	$160.10
Purchase #7	$196.27	6.253%	$208.5428	$208.54	$208.55	$208.50
7 purchase totals =	$853.71		$912.6858	$912.68	$912.65	$912.70