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	$199.57	11.409%	$222.3389	$222.34	$222.35	$222.30
Purchase #2	$129.50	10.399%	$142.9667	$142.97	$142.95	$143.00
Purchase #3	$171.33	9.290%	$187.2466	$187.25	$187.25	$187.20
Purchase #4	$201.60	13.605%	$229.0277	$229.03	$229.05	$229.00
Purchase #5	$83.55	7.113%	$89.4929	$89.49	$89.50	$89.50
Purchase #6	$187.52	9.247%	$204.86	$204.86	$204.85	$204.90
Purchase #7	$133.25	10.727%	$147.5437	$147.54	$147.55	$147.50
7 purchase totals =	$1,106.32		$1,223.4765	$1,223.48	$1,223.50	$1,223.40