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	$31.82	3.144%	$32.8204	$32.82	$32.80	$32.80
Purchase #2	$131.36	7.617%	$141.3657	$141.37	$141.35	$141.40
Purchase #3	$222.91	6.517%	$237.437	$237.44	$237.45	$237.40
Purchase #4	$206.71	8.763%	$224.824	$224.82	$224.80	$224.80
Purchase #5	$153.61	7.582%	$165.2567	$165.26	$165.25	$165.30
Purchase #6	$66.64	8.239%	$72.1305	$72.13	$72.15	$72.10
Purchase #7	$197.89	6.249%	$210.2561	$210.26	$210.25	$210.30
7 purchase totals =	$1,010.94		$1,084.0904	$1,084.10	$1,084.05	$1,084.10