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	$99.62	12.857%	$112.4281	$112.43	$112.45	$112.40
Purchase #2	$66.84	8.141%	$72.2814	$72.28	$72.30	$72.30
Purchase #3	$53.43	7.369%	$57.3673	$57.37	$57.35	$57.40
Purchase #4	$25.76	10.329%	$28.4208	$28.42	$28.40	$28.40
Purchase #5	$26.98	7.241%	$28.9336	$28.93	$28.95	$28.90
Purchase #6	$29.53	6.281%	$31.3848	$31.38	$31.40	$31.40
Purchase #7	$94.34	7.743%	$101.6447	$101.64	$101.65	$101.60
7 purchase totals =	$396.50		$432.4607	$432.45	$432.50	$432.40