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	$205.30	9.454%	$224.7091	$224.71	$224.70	$224.70
Purchase #2	$248.50	13.242%	$281.4064	$281.41	$281.40	$281.40
Purchase #3	$99.92	9.695%	$109.6072	$109.61	$109.60	$109.60
Purchase #4	$98.70	12.589%	$111.1253	$111.13	$111.15	$111.10
Purchase #5	$125.61	9.567%	$137.6271	$137.63	$137.65	$137.60
Purchase #6	$42.28	3.358%	$43.6998	$43.70	$43.70	$43.70
Purchase #7	$250.48	4.536%	$261.8418	$261.84	$261.85	$261.80
7 purchase totals =	$1,070.79		$1,170.0167	$1,170.03	$1,170.05	$1,169.90