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	$212.90	7.677%	$229.2443	$229.24	$229.25	$229.20
Purchase #2	$152.90	13.360%	$173.3274	$173.33	$173.35	$173.30
Purchase #3	$142.56	3.421%	$147.437	$147.44	$147.45	$147.40
Purchase #4	$148.98	10.331%	$164.3711	$164.37	$164.35	$164.40
Purchase #5	$15.81	3.130%	$16.3049	$16.30	$16.30	$16.30
Purchase #6	$150.63	9.452%	$164.8675	$164.87	$164.85	$164.90
Purchase #7	$91.87	9.351%	$100.4608	$100.46	$100.45	$100.50
7 purchase totals =	$915.65		$996.0130	$996.01	$996.00	$996.00