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	$104.98	5.783%	$111.051	$111.05	$111.05	$111.10
Purchase #2	$161.32	13.399%	$182.9353	$182.94	$182.95	$182.90
Purchase #3	$55.46	8.217%	$60.0171	$60.02	$60.00	$60.00
Purchase #4	$201.55	4.738%	$211.0994	$211.10	$211.10	$211.10
Purchase #5	$90.45	10.330%	$99.7935	$99.79	$99.80	$99.80
Purchase #6	$189.83	8.408%	$205.7909	$205.79	$205.80	$205.80
Purchase #7	$34.83	7.853%	$37.5652	$37.57	$37.55	$37.60
7 purchase totals =	$838.42		$908.2524	$908.26	$908.25	$908.30