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	$90.92	9.337%	$99.4092	$99.41	$99.40	$99.40
Purchase #2	$228.51	9.517%	$250.2573	$250.26	$250.25	$250.30
Purchase #3	$33.54	4.241%	$34.9624	$34.96	$34.95	$35.00
Purchase #4	$194.67	12.692%	$219.3775	$219.38	$219.40	$219.40
Purchase #5	$210.48	5.643%	$222.3574	$222.36	$222.35	$222.40
Purchase #6	$167.40	5.462%	$176.5434	$176.54	$176.55	$176.50
Purchase #7	$222.34	7.250%	$238.4597	$238.46	$238.45	$238.50
7 purchase totals =	$1,147.86		$1,241.3669	$1,241.37	$1,241.35	$1,241.50