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	$22.49	10.248%	$24.7948	$24.79	$24.80	$24.80
Purchase #2	$118.91	11.804%	$132.9461	$132.95	$132.95	$132.90
Purchase #3	$231.99	8.538%	$251.7973	$251.80	$251.80	$251.80
Purchase #4	$37.33	7.159%	$40.0025	$40.00	$40.00	$40.00
Purchase #5	$158.83	5.812%	$168.0612	$168.06	$168.05	$168.10
Purchase #6	$158.36	4.526%	$165.5274	$165.53	$165.55	$165.50
Purchase #7	$211.77	10.406%	$233.8068	$233.81	$233.80	$233.80
7 purchase totals =	$939.68		$1,016.9361	$1,016.94	$1,016.95	$1,016.90