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	$25.88	13.164%	$29.2868	$29.29	$29.30	$29.30
Purchase #2	$232.89	11.271%	$259.139	$259.14	$259.15	$259.10
Purchase #3	$194.42	12.578%	$218.8741	$218.87	$218.85	$218.90
Purchase #4	$141.40	10.176%	$155.7889	$155.79	$155.80	$155.80
Purchase #5	$104.76	11.781%	$117.1018	$117.10	$117.10	$117.10
Purchase #6	$78.54	5.556%	$82.9037	$82.90	$82.90	$82.90
Purchase #7	$162.55	5.789%	$171.96	$171.96	$171.95	$172.00
7 purchase totals =	$940.44		$1,035.0543	$1,035.05	$1,035.05	$1,035.10