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	$149.85	5.851%	$158.6177	$158.62	$158.60	$158.60
Purchase #2	$40.43	4.458%	$42.2324	$42.23	$42.25	$42.20
Purchase #3	$140.35	5.317%	$147.8124	$147.81	$147.80	$147.80
Purchase #4	$147.91	11.470%	$164.8753	$164.88	$164.90	$164.90
Purchase #5	$43.47	7.795%	$46.8585	$46.86	$46.85	$46.90
Purchase #6	$222.82	12.746%	$251.2206	$251.22	$251.20	$251.20
Purchase #7	$38.28	11.592%	$42.7174	$42.72	$42.70	$42.70
7 purchase totals =	$783.11		$854.3343	$854.34	$854.30	$854.30