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	$68.34	5.670%	$72.2149	$72.21	$72.20	$72.20
Purchase #2	$62.86	11.766%	$70.2561	$70.26	$70.25	$70.30
Purchase #3	$100.98	10.569%	$111.6526	$111.65	$111.65	$111.70
Purchase #4	$160.87	4.792%	$168.5789	$168.58	$168.60	$168.60
Purchase #5	$106.59	8.330%	$115.4689	$115.47	$115.45	$115.50
Purchase #6	$38.96	10.614%	$43.0952	$43.10	$43.10	$43.10
Purchase #7	$202.94	4.556%	$212.1859	$212.19	$212.20	$212.20
7 purchase totals =	$741.54		$793.4525	$793.46	$793.45	$793.60