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	$90.26	9.300%	$98.6542	$98.65	$98.65	$98.70
Purchase #2	$193.63	9.282%	$211.6027	$211.60	$211.60	$211.60
Purchase #3	$86.94	4.181%	$90.575	$90.58	$90.60	$90.60
Purchase #4	$97.34	7.450%	$104.5918	$104.59	$104.60	$104.60
Purchase #5	$58.55	7.805%	$63.1198	$63.12	$63.10	$63.10
Purchase #6	$92.91	8.131%	$100.4645	$100.46	$100.45	$100.50
Purchase #7	$36.68	6.801%	$39.1746	$39.17	$39.15	$39.20
7 purchase totals =	$656.31		$708.1826	$708.17	$708.15	$708.30