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	$209.42	9.358%	$229.0175	$229.02	$229.00	$229.00
Purchase #2	$34.53	7.340%	$37.0645	$37.06	$37.05	$37.10
Purchase #3	$104.31	4.730%	$109.2439	$109.24	$109.25	$109.20
Purchase #4	$148.82	13.818%	$169.3839	$169.38	$169.40	$169.40
Purchase #5	$116.49	4.371%	$121.5818	$121.58	$121.60	$121.60
Purchase #6	$165.34	10.342%	$182.4395	$182.44	$182.45	$182.40
Purchase #7	$149.60	5.498%	$157.825	$157.83	$157.85	$157.80
7 purchase totals =	$928.51		$1,006.5561	$1,006.55	$1,006.60	$1,006.50