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	$152.98	8.218%	$165.5519	$165.55	$165.55	$165.60
Purchase #2	$189.59	4.194%	$197.5414	$197.54	$197.55	$197.50
Purchase #3	$112.79	9.540%	$123.5502	$123.55	$123.55	$123.60
Purchase #4	$130.81	8.139%	$141.4566	$141.46	$141.45	$141.50
Purchase #5	$35.61	4.870%	$37.3442	$37.34	$37.35	$37.30
Purchase #6	$120.93	8.369%	$131.0506	$131.05	$131.05	$131.10
Purchase #7	$50.73	4.471%	$52.9981	$53.00	$53.00	$53.00
7 purchase totals =	$793.44		$849.4930	$849.49	$849.50	$849.60