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	$102.61	10.403%	$113.2845	$113.28	$113.30	$113.30
Purchase #2	$112.92	5.310%	$118.9161	$118.92	$118.90	$118.90
Purchase #3	$186.59	8.374%	$202.215	$202.22	$202.20	$202.20
Purchase #4	$111.77	10.401%	$123.3952	$123.40	$123.40	$123.40
Purchase #5	$179.76	6.706%	$191.8147	$191.81	$191.80	$191.80
Purchase #6	$64.88	12.188%	$72.7876	$72.79	$72.80	$72.80
Purchase #7	$97.94	11.634%	$109.3343	$109.33	$109.35	$109.30
7 purchase totals =	$856.47		$931.7474	$931.75	$931.75	$931.70