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	$184.77	3.193%	$190.6697	$190.67	$190.65	$190.70
Purchase #2	$16.61	12.142%	$18.6268	$18.63	$18.65	$18.60
Purchase #3	$113.48	4.396%	$118.4686	$118.47	$118.45	$118.50
Purchase #4	$154.43	6.213%	$164.0247	$164.02	$164.00	$164.00
Purchase #5	$104.30	13.725%	$118.6152	$118.62	$118.60	$118.60
Purchase #6	$149.77	4.435%	$156.4123	$156.41	$156.40	$156.40
Purchase #7	$248.36	9.320%	$271.5072	$271.51	$271.50	$271.50
7 purchase totals =	$971.72		$1,038.3245	$1,038.33	$1,038.25	$1,038.30