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	$203.88	9.562%	$223.375	$223.38	$223.40	$223.40
Purchase #2	$57.62	11.725%	$64.3759	$64.38	$64.40	$64.40
Purchase #3	$132.93	9.376%	$145.3935	$145.39	$145.40	$145.40
Purchase #4	$240.30	9.114%	$262.2009	$262.20	$262.20	$262.20
Purchase #5	$27.69	5.822%	$29.3021	$29.30	$29.30	$29.30
Purchase #6	$100.86	12.306%	$113.2718	$113.27	$113.25	$113.30
Purchase #7	$53.37	11.703%	$59.6159	$59.62	$59.60	$59.60
7 purchase totals =	$816.65		$897.5351	$897.54	$897.55	$897.60