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	$246.35	11.173%	$273.8747	$273.87	$273.85	$273.90
Purchase #2	$24.56	5.423%	$25.8919	$25.89	$25.90	$25.90
Purchase #3	$201.44	9.828%	$221.2375	$221.24	$221.25	$221.20
Purchase #4	$153.96	4.169%	$160.3786	$160.38	$160.40	$160.40
Purchase #5	$89.59	12.333%	$100.6391	$100.64	$100.65	$100.60
Purchase #6	$131.87	7.487%	$141.7431	$141.74	$141.75	$141.70
Purchase #7	$66.31	9.280%	$72.4636	$72.46	$72.45	$72.50
7 purchase totals =	$914.08		$996.2285	$996.22	$996.25	$996.20