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	$116.28	11.212%	$129.3173	$129.32	$129.30	$129.30
Purchase #2	$144.52	6.217%	$153.5048	$153.50	$153.50	$153.50
Purchase #3	$71.78	6.270%	$76.2806	$76.28	$76.30	$76.30
Purchase #4	$130.40	7.821%	$140.5986	$140.60	$140.60	$140.60
Purchase #5	$151.98	10.872%	$168.5033	$168.50	$168.50	$168.50
Purchase #6	$151.58	6.118%	$160.8537	$160.85	$160.85	$160.90
Purchase #7	$166.26	3.314%	$171.7699	$171.77	$171.75	$171.80
7 purchase totals =	$932.80		$1,000.8282	$1,000.82	$1,000.80	$1,000.90