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	$160.77	4.394%	$167.8342	$167.83	$167.85	$167.80
Purchase #2	$129.28	6.652%	$137.8797	$137.88	$137.90	$137.90
Purchase #3	$140.96	4.586%	$147.4244	$147.42	$147.40	$147.40
Purchase #4	$168.47	12.737%	$189.928	$189.93	$189.95	$189.90
Purchase #5	$95.88	4.637%	$100.326	$100.33	$100.35	$100.30
Purchase #6	$228.44	10.231%	$251.8117	$251.81	$251.80	$251.80
Purchase #7	$24.60	10.626%	$27.214	$27.21	$27.20	$27.20
7 purchase totals =	$948.40		$1,022.4180	$1,022.41	$1,022.45	$1,022.30