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	$160.97	11.425%	$179.3608	$179.36	$179.35	$179.40
Purchase #2	$114.71	10.403%	$126.6433	$126.64	$126.65	$126.60
Purchase #3	$140.37	9.124%	$153.1774	$153.18	$153.20	$153.20
Purchase #4	$154.26	6.649%	$164.5167	$164.52	$164.50	$164.50
Purchase #5	$197.77	12.445%	$222.3825	$222.38	$222.40	$222.40
Purchase #6	$120.63	5.330%	$127.0596	$127.06	$127.05	$127.10
Purchase #7	$166.35	9.495%	$182.1449	$182.14	$182.15	$182.10
7 purchase totals =	$1,055.06		$1,155.2852	$1,155.28	$1,155.30	$1,155.30