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	$103.86	12.798%	$117.152	$117.15	$117.15	$117.20
Purchase #2	$25.67	5.494%	$27.0803	$27.08	$27.10	$27.10
Purchase #3	$140.79	8.135%	$152.2433	$152.24	$152.25	$152.20
Purchase #4	$232.32	4.307%	$242.326	$242.33	$242.35	$242.30
Purchase #5	$72.89	13.194%	$82.5071	$82.51	$82.50	$82.50
Purchase #6	$234.51	3.536%	$242.8023	$242.80	$242.80	$242.80
Purchase #7	$200.87	11.413%	$223.7953	$223.80	$223.80	$223.80
7 purchase totals =	$1,010.91		$1,087.9063	$1,087.91	$1,087.95	$1,087.90