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	$245.75	11.438%	$273.8589	$273.86	$273.85	$273.90
Purchase #2	$90.97	10.709%	$100.712	$100.71	$100.70	$100.70
Purchase #3	$208.38	10.798%	$230.8809	$230.88	$230.90	$230.90
Purchase #4	$82.70	11.331%	$92.0707	$92.07	$92.05	$92.10
Purchase #5	$141.44	7.821%	$152.502	$152.50	$152.50	$152.50
Purchase #6	$223.78	6.478%	$238.2765	$238.28	$238.30	$238.30
Purchase #7	$58.82	3.666%	$60.9763	$60.98	$61.00	$61.00
7 purchase totals =	$1,051.84		$1,149.2773	$1,149.28	$1,149.30	$1,149.40