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	$64.58	13.285%	$73.1595	$73.16	$73.15	$73.20
Purchase #2	$108.62	13.860%	$123.6747	$123.67	$123.65	$123.70
Purchase #3	$210.64	11.792%	$235.4787	$235.48	$235.50	$235.50
Purchase #4	$241.44	12.592%	$271.8421	$271.84	$271.85	$271.80
Purchase #5	$114.45	3.826%	$118.8289	$118.83	$118.85	$118.80
Purchase #6	$32.98	7.138%	$35.3341	$35.33	$35.35	$35.30
Purchase #7	$162.82	5.124%	$171.1629	$171.16	$171.15	$171.20
7 purchase totals =	$935.53		$1,029.4809	$1,029.47	$1,029.50	$1,029.50