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	$171.44	11.610%	$191.3442	$191.34	$191.35	$191.30
Purchase #2	$132.52	9.750%	$145.4407	$145.44	$145.45	$145.40
Purchase #3	$196.80	3.794%	$204.2666	$204.27	$204.25	$204.30
Purchase #4	$245.96	10.409%	$271.562	$271.56	$271.55	$271.60
Purchase #5	$61.42	10.482%	$67.858	$67.86	$67.85	$67.90
Purchase #6	$162.69	7.244%	$174.4753	$174.48	$174.50	$174.50
Purchase #7	$221.60	6.301%	$235.563	$235.56	$235.55	$235.60
7 purchase totals =	$1,192.43		$1,290.5098	$1,290.51	$1,290.50	$1,290.60