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	$72.48	8.669%	$78.7633	$78.76	$78.75	$78.80
Purchase #2	$221.32	3.270%	$228.5572	$228.56	$228.55	$228.60
Purchase #3	$146.74	13.484%	$166.5264	$166.53	$166.55	$166.50
Purchase #4	$121.56	12.414%	$136.6505	$136.65	$136.65	$136.70
Purchase #5	$81.42	5.125%	$85.5928	$85.59	$85.60	$85.60
Purchase #6	$249.30	4.811%	$261.2938	$261.29	$261.30	$261.30
Purchase #7	$202.87	12.377%	$227.9792	$227.98	$228.00	$228.00
7 purchase totals =	$1,095.69		$1,185.3632	$1,185.36	$1,185.40	$1,185.50