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	$207.59	3.234%	$214.3035	$214.30	$214.30	$214.30
Purchase #2	$168.82	4.704%	$176.7613	$176.76	$176.75	$176.80
Purchase #3	$28.82	12.453%	$32.409	$32.41	$32.40	$32.40
Purchase #4	$181.45	3.660%	$188.0911	$188.09	$188.10	$188.10
Purchase #5	$206.45	10.214%	$227.5368	$227.54	$227.55	$227.50
Purchase #6	$91.62	6.778%	$97.83	$97.83	$97.85	$97.80
Purchase #7	$81.71	9.327%	$89.3311	$89.33	$89.35	$89.30
7 purchase totals =	$966.46		$1,026.2628	$1,026.26	$1,026.30	$1,026.20