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	$43.97	8.146%	$47.5518	$47.55	$47.55	$47.60
Purchase #2	$70.83	13.589%	$80.4551	$80.46	$80.45	$80.50
Purchase #3	$214.86	3.128%	$221.5808	$221.58	$221.60	$221.60
Purchase #4	$108.34	11.197%	$120.4708	$120.47	$120.45	$120.50
Purchase #5	$136.69	7.436%	$146.8543	$146.85	$146.85	$146.90
Purchase #6	$108.33	3.315%	$111.9211	$111.92	$111.90	$111.90
Purchase #7	$96.58	7.791%	$104.1045	$104.10	$104.10	$104.10
7 purchase totals =	$779.60		$832.9384	$832.93	$832.90	$833.10