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	$93.54	9.304%	$102.243	$102.24	$102.25	$102.20
Purchase #2	$250.62	3.117%	$258.4318	$258.43	$258.45	$258.40
Purchase #3	$97.29	7.242%	$104.3357	$104.34	$104.35	$104.30
Purchase #4	$45.62	13.806%	$51.9183	$51.92	$51.90	$51.90
Purchase #5	$175.76	8.729%	$191.1021	$191.10	$191.10	$191.10
Purchase #6	$48.68	9.802%	$53.4516	$53.45	$53.45	$53.50
Purchase #7	$110.29	11.618%	$123.1035	$123.10	$123.10	$123.10
7 purchase totals =	$821.80		$884.5860	$884.58	$884.60	$884.50