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	$136.81	9.774%	$150.1818	$150.18	$150.20	$150.20
Purchase #2	$185.30	5.138%	$194.8207	$194.82	$194.80	$194.80
Purchase #3	$155.46	8.365%	$168.4642	$168.46	$168.45	$168.50
Purchase #4	$28.89	13.449%	$32.7754	$32.78	$32.80	$32.80
Purchase #5	$113.25	11.307%	$126.0552	$126.06	$126.05	$126.10
Purchase #6	$91.55	13.202%	$103.6364	$103.64	$103.65	$103.60
Purchase #7	$194.63	12.269%	$218.5092	$218.51	$218.50	$218.50
7 purchase totals =	$905.89		$994.4429	$994.45	$994.45	$994.50