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	$96.96	8.619%	$105.317	$105.32	$105.30	$105.30
Purchase #2	$149.51	8.689%	$162.5009	$162.50	$162.50	$162.50
Purchase #3	$199.45	5.438%	$210.2961	$210.30	$210.30	$210.30
Purchase #4	$230.45	3.504%	$238.525	$238.53	$238.55	$238.50
Purchase #5	$32.25	9.637%	$35.3579	$35.36	$35.35	$35.40
Purchase #6	$123.49	5.689%	$130.5153	$130.52	$130.50	$130.50
Purchase #7	$165.87	5.725%	$175.3661	$175.37	$175.35	$175.40
7 purchase totals =	$997.98		$1,057.8783	$1,057.90	$1,057.85	$1,057.90