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	$169.41	11.200%	$188.3839	$188.38	$188.40	$188.40
Purchase #2	$100.56	11.356%	$111.9796	$111.98	$112.00	$112.00
Purchase #3	$120.54	6.395%	$128.2485	$128.25	$128.25	$128.20
Purchase #4	$126.32	4.543%	$132.0587	$132.06	$132.05	$132.10
Purchase #5	$35.41	5.553%	$37.3763	$37.38	$37.40	$37.40
Purchase #6	$117.35	5.633%	$123.9603	$123.96	$123.95	$124.00
Purchase #7	$202.35	8.801%	$220.1588	$220.16	$220.15	$220.20
7 purchase totals =	$871.94		$942.1661	$942.17	$942.20	$942.30