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	$169.49	6.242%	$180.0696	$180.07	$180.05	$180.10
Purchase #2	$217.90	8.267%	$235.9138	$235.91	$235.90	$235.90
Purchase #3	$109.82	4.504%	$114.7663	$114.77	$114.75	$114.80
Purchase #4	$182.60	6.540%	$194.542	$194.54	$194.55	$194.50
Purchase #5	$177.77	4.222%	$185.2754	$185.28	$185.30	$185.30
Purchase #6	$43.37	5.356%	$45.6929	$45.69	$45.70	$45.70
Purchase #7	$75.60	12.578%	$85.109	$85.11	$85.10	$85.10
7 purchase totals =	$976.55		$1,041.3690	$1,041.37	$1,041.35	$1,041.40