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	$160.41	7.141%	$171.8649	$171.86	$171.85	$171.90
Purchase #2	$152.52	7.312%	$163.6723	$163.67	$163.65	$163.70
Purchase #3	$215.47	4.202%	$224.524	$224.52	$224.50	$224.50
Purchase #4	$113.61	10.260%	$125.2664	$125.27	$125.25	$125.30
Purchase #5	$122.96	3.645%	$127.4419	$127.44	$127.45	$127.40
Purchase #6	$105.69	3.351%	$109.2317	$109.23	$109.25	$109.20
Purchase #7	$223.85	4.128%	$233.0905	$233.09	$233.10	$233.10
7 purchase totals =	$1,094.51		$1,155.0917	$1,155.08	$1,155.05	$1,155.10