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	$53.36	11.133%	$59.3006	$59.30	$59.30	$59.30
Purchase #2	$196.46	10.271%	$216.6384	$216.64	$216.65	$216.60
Purchase #3	$95.42	4.400%	$99.6185	$99.62	$99.60	$99.60
Purchase #4	$203.62	11.686%	$227.415	$227.42	$227.40	$227.40
Purchase #5	$117.85	8.699%	$128.1018	$128.10	$128.10	$128.10
Purchase #6	$232.42	12.396%	$261.2308	$261.23	$261.25	$261.20
Purchase #7	$38.52	13.712%	$43.8019	$43.80	$43.80	$43.80
7 purchase totals =	$937.65		$1,036.1070	$1,036.11	$1,036.10	$1,036.00