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	$33.91	3.458%	$35.0826	$35.08	$35.10	$35.10
Purchase #2	$37.48	3.807%	$38.9069	$38.91	$38.90	$38.90
Purchase #3	$30.66	5.826%	$32.4463	$32.45	$32.45	$32.40
Purchase #4	$92.77	10.782%	$102.7725	$102.77	$102.75	$102.80
Purchase #5	$86.64	4.191%	$90.2711	$90.27	$90.25	$90.30
Purchase #6	$26.56	6.726%	$28.3464	$28.35	$28.35	$28.30
Purchase #7	$133.58	5.718%	$141.2181	$141.22	$141.20	$141.20
7 purchase totals =	$441.60		$469.0439	$469.05	$469.00	$469.00