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	$192.81	3.711%	$199.9652	$199.97	$199.95	$200.00
Purchase #2	$114.39	3.566%	$118.4691	$118.47	$118.45	$118.50
Purchase #3	$64.85	11.240%	$72.1391	$72.14	$72.15	$72.10
Purchase #4	$234.85	8.266%	$254.2627	$254.26	$254.25	$254.30
Purchase #5	$174.98	11.160%	$194.5078	$194.51	$194.50	$194.50
Purchase #6	$113.90	4.294%	$118.7909	$118.79	$118.80	$118.80
Purchase #7	$48.77	7.564%	$52.459	$52.46	$52.45	$52.50
7 purchase totals =	$944.55		$1,010.5938	$1,010.60	$1,010.55	$1,010.70