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	$208.85	10.737%	$231.2742	$231.27	$231.25	$231.30
Purchase #2	$101.74	3.484%	$105.2846	$105.28	$105.30	$105.30
Purchase #3	$98.74	3.674%	$102.3677	$102.37	$102.35	$102.40
Purchase #4	$86.53	6.224%	$91.9156	$91.92	$91.90	$91.90
Purchase #5	$157.34	4.811%	$164.9096	$164.91	$164.90	$164.90
Purchase #6	$111.82	10.163%	$123.1843	$123.18	$123.20	$123.20
Purchase #7	$94.91	12.731%	$106.993	$106.99	$107.00	$107.00
7 purchase totals =	$859.93		$925.9290	$925.92	$925.90	$926.00