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	$94.86	10.260%	$104.5926	$104.59	$104.60	$104.60
Purchase #2	$215.64	13.440%	$244.622	$244.62	$244.60	$244.60
Purchase #3	$234.86	6.356%	$249.7877	$249.79	$249.80	$249.80
Purchase #4	$48.90	10.397%	$53.9841	$53.98	$54.00	$54.00
Purchase #5	$181.33	3.228%	$187.1833	$187.18	$187.20	$187.20
Purchase #6	$230.69	10.561%	$255.0532	$255.05	$255.05	$255.10
Purchase #7	$65.85	8.429%	$71.4005	$71.40	$71.40	$71.40
7 purchase totals =	$1,072.13		$1,166.6234	$1,166.61	$1,166.65	$1,166.70