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	$90.77	6.784%	$96.9278	$96.93	$96.95	$96.90
Purchase #2	$19.73	7.436%	$21.1971	$21.20	$21.20	$21.20
Purchase #3	$72.36	11.306%	$80.541	$80.54	$80.55	$80.50
Purchase #4	$100.63	13.564%	$114.2795	$114.28	$114.30	$114.30
Purchase #5	$94.34	9.812%	$103.5966	$103.60	$103.60	$103.60
Purchase #6	$162.94	11.604%	$181.8476	$181.85	$181.85	$181.80
Purchase #7	$211.82	10.732%	$234.5525	$234.55	$234.55	$234.60
7 purchase totals =	$752.59		$832.9421	$832.95	$833.00	$832.90