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	$162.75	6.527%	$173.3727	$173.37	$173.35	$173.40
Purchase #2	$10.51	10.583%	$11.6223	$11.62	$11.60	$11.60
Purchase #3	$203.82	9.471%	$223.1238	$223.12	$223.10	$223.10
Purchase #4	$34.41	4.216%	$35.8607	$35.86	$35.85	$35.90
Purchase #5	$30.96	7.602%	$33.3136	$33.31	$33.30	$33.30
Purchase #6	$152.57	12.187%	$171.1637	$171.16	$171.15	$171.20
Purchase #7	$72.25	6.141%	$76.6869	$76.69	$76.70	$76.70
7 purchase totals =	$667.27		$725.1437	$725.13	$725.05	$725.20