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	$162.69	5.116%	$171.0132	$171.01	$171.00	$171.00
Purchase #2	$226.30	5.561%	$238.8845	$238.88	$238.90	$238.90
Purchase #3	$247.32	9.683%	$271.268	$271.27	$271.25	$271.30
Purchase #4	$5.28	4.163%	$5.4998	$5.50	$5.50	$5.50
Purchase #5	$63.74	6.233%	$67.7129	$67.71	$67.70	$67.70
Purchase #6	$148.48	12.359%	$166.8306	$166.83	$166.85	$166.80
Purchase #7	$135.97	4.340%	$141.8711	$141.87	$141.85	$141.90
7 purchase totals =	$989.78		$1,063.0801	$1,063.07	$1,063.05	$1,063.10