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	$59.49	13.201%	$67.3433	$67.34	$67.35	$67.30
Purchase #2	$10.56	3.364%	$10.9152	$10.92	$10.90	$10.90
Purchase #3	$84.33	12.376%	$94.7667	$94.77	$94.75	$94.80
Purchase #4	$209.26	11.723%	$233.7915	$233.79	$233.80	$233.80
Purchase #5	$133.68	11.375%	$148.8861	$148.89	$148.90	$148.90
Purchase #6	$200.60	5.294%	$211.2198	$211.22	$211.20	$211.20
Purchase #7	$166.92	3.407%	$172.607	$172.61	$172.60	$172.60
7 purchase totals =	$864.84		$939.5296	$939.54	$939.50	$939.50