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	$156.56	4.447%	$163.5222	$163.52	$163.50	$163.50
Purchase #2	$168.43	9.286%	$184.0704	$184.07	$184.05	$184.10
Purchase #3	$19.70	8.238%	$21.3229	$21.32	$21.30	$21.30
Purchase #4	$113.56	11.728%	$126.8783	$126.88	$126.90	$126.90
Purchase #5	$38.63	4.474%	$40.3583	$40.36	$40.35	$40.40
Purchase #6	$117.30	11.218%	$130.4587	$130.46	$130.45	$130.50
Purchase #7	$141.47	12.312%	$158.8878	$158.89	$158.90	$158.90
7 purchase totals =	$755.65		$825.4986	$825.50	$825.45	$825.60