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	$116.54	5.587%	$123.0511	$123.05	$123.05	$123.10
Purchase #2	$114.92	7.261%	$123.2643	$123.26	$123.25	$123.30
Purchase #3	$91.38	7.872%	$98.5734	$98.57	$98.55	$98.60
Purchase #4	$49.82	9.477%	$54.5414	$54.54	$54.55	$54.50
Purchase #5	$167.76	6.473%	$178.6191	$178.62	$178.60	$178.60
Purchase #6	$209.28	8.558%	$227.1902	$227.19	$227.20	$227.20
Purchase #7	$210.93	10.472%	$233.0186	$233.02	$233.00	$233.00
7 purchase totals =	$960.63		$1,038.2581	$1,038.25	$1,038.20	$1,038.30