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	$152.71	6.518%	$162.6636	$162.66	$162.65	$162.70
Purchase #2	$49.71	7.785%	$53.5799	$53.58	$53.60	$53.60
Purchase #3	$136.27	10.398%	$150.4394	$150.44	$150.45	$150.40
Purchase #4	$51.36	7.702%	$55.3157	$55.32	$55.30	$55.30
Purchase #5	$64.62	9.806%	$70.9566	$70.96	$70.95	$71.00
Purchase #6	$97.70	8.146%	$105.6586	$105.66	$105.65	$105.70
Purchase #7	$95.41	3.264%	$98.5242	$98.52	$98.50	$98.50
7 purchase totals =	$647.78		$697.1380	$697.14	$697.10	$697.20