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	$116.63	5.490%	$123.033	$123.03	$123.05	$123.00
Purchase #2	$138.31	7.410%	$148.5588	$148.56	$148.55	$148.60
Purchase #3	$64.45	5.471%	$67.9761	$67.98	$68.00	$68.00
Purchase #4	$149.84	3.188%	$154.6169	$154.62	$154.60	$154.60
Purchase #5	$83.76	7.269%	$89.8485	$89.85	$89.85	$89.80
Purchase #6	$97.73	5.795%	$103.3935	$103.39	$103.40	$103.40
Purchase #7	$158.25	4.534%	$165.4251	$165.43	$165.45	$165.40
7 purchase totals =	$808.97		$852.8519	$852.86	$852.90	$852.80