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	$20.92	6.573%	$22.2951	$22.30	$22.30	$22.30
Purchase #2	$215.72	7.161%	$231.1677	$231.17	$231.15	$231.20
Purchase #3	$224.89	6.874%	$240.3489	$240.35	$240.35	$240.30
Purchase #4	$226.53	13.153%	$256.3255	$256.33	$256.35	$256.30
Purchase #5	$112.80	3.860%	$117.1541	$117.15	$117.15	$117.20
Purchase #6	$35.48	6.119%	$37.651	$37.65	$37.65	$37.70
Purchase #7	$34.60	9.780%	$37.9839	$37.98	$38.00	$38.00
7 purchase totals =	$870.94		$942.9262	$942.93	$942.95	$943.00