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	$23.56	4.349%	$24.5846	$24.58	$24.60	$24.60
Purchase #2	$92.87	4.238%	$96.8058	$96.81	$96.80	$96.80
Purchase #3	$81.54	9.666%	$89.4217	$89.42	$89.40	$89.40
Purchase #4	$231.60	6.139%	$245.8179	$245.82	$245.80	$245.80
Purchase #5	$172.76	10.454%	$190.8203	$190.82	$190.80	$190.80
Purchase #6	$171.82	12.413%	$193.148	$193.15	$193.15	$193.10
Purchase #7	$167.42	11.105%	$186.012	$186.01	$186.00	$186.00
7 purchase totals =	$941.57		$1,026.6103	$1,026.61	$1,026.55	$1,026.50