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	$173.45	4.502%	$181.2587	$181.26	$181.25	$181.30
Purchase #2	$75.98	8.126%	$82.1541	$82.15	$82.15	$82.20
Purchase #3	$109.85	12.260%	$123.3176	$123.32	$123.30	$123.30
Purchase #4	$53.87	10.485%	$59.5183	$59.52	$59.50	$59.50
Purchase #5	$178.54	6.198%	$189.6059	$189.61	$189.60	$189.60
Purchase #6	$243.63	5.859%	$257.9043	$257.90	$257.90	$257.90
Purchase #7	$110.52	5.122%	$116.1808	$116.18	$116.20	$116.20
7 purchase totals =	$945.84		$1,009.9397	$1,009.94	$1,009.90	$1,010.00