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	$169.34	10.494%	$187.1105	$187.11	$187.10	$187.10
Purchase #2	$42.28	12.234%	$47.4525	$47.45	$47.45	$47.50
Purchase #3	$38.56	3.392%	$39.868	$39.87	$39.85	$39.90
Purchase #4	$40.80	3.278%	$42.1374	$42.14	$42.15	$42.10
Purchase #5	$123.95	3.334%	$128.0825	$128.08	$128.10	$128.10
Purchase #6	$61.82	10.537%	$68.334	$68.33	$68.35	$68.30
Purchase #7	$169.94	7.245%	$182.2522	$182.25	$182.25	$182.30
7 purchase totals =	$646.69		$695.2371	$695.23	$695.25	$695.30