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	$128.67	10.463%	$142.1327	$142.13	$142.15	$142.10
Purchase #2	$153.98	7.520%	$165.5593	$165.56	$165.55	$165.60
Purchase #3	$67.63	11.702%	$75.5441	$75.54	$75.55	$75.50
Purchase #4	$104.82	4.776%	$109.8262	$109.83	$109.85	$109.80
Purchase #5	$215.37	5.786%	$227.8313	$227.83	$227.85	$227.80
Purchase #6	$218.65	12.866%	$246.7815	$246.78	$246.80	$246.80
Purchase #7	$86.62	5.194%	$91.119	$91.12	$91.10	$91.10
7 purchase totals =	$975.74		$1,058.7941	$1,058.79	$1,058.85	$1,058.70