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	$177.46	4.564%	$185.5593	$185.56	$185.55	$185.60
Purchase #2	$147.89	11.231%	$164.4995	$164.50	$164.50	$164.50
Purchase #3	$81.49	4.684%	$85.307	$85.31	$85.30	$85.30
Purchase #4	$69.86	11.222%	$77.6997	$77.70	$77.70	$77.70
Purchase #5	$138.31	7.861%	$149.1825	$149.18	$149.20	$149.20
Purchase #6	$125.35	11.356%	$139.5847	$139.58	$139.60	$139.60
Purchase #7	$43.36	7.469%	$46.5986	$46.60	$46.60	$46.60
7 purchase totals =	$783.72		$848.4313	$848.43	$848.45	$848.50