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	$150.79	7.532%	$162.1475	$162.15	$162.15	$162.10
Purchase #2	$203.28	3.291%	$209.9699	$209.97	$209.95	$210.00
Purchase #3	$61.29	12.370%	$68.8716	$68.87	$68.85	$68.90
Purchase #4	$109.91	8.476%	$119.226	$119.23	$119.25	$119.20
Purchase #5	$103.51	5.352%	$109.0499	$109.05	$109.05	$109.00
Purchase #6	$233.52	11.539%	$260.4659	$260.47	$260.45	$260.50
Purchase #7	$102.89	6.737%	$109.8217	$109.82	$109.80	$109.80
7 purchase totals =	$965.19		$1,039.5525	$1,039.56	$1,039.50	$1,039.50