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	$102.48	7.204%	$109.8627	$109.86	$109.85	$109.90
Purchase #2	$196.88	5.406%	$207.5233	$207.52	$207.50	$207.50
Purchase #3	$37.79	12.399%	$42.4756	$42.48	$42.50	$42.50
Purchase #4	$239.55	4.452%	$250.2148	$250.21	$250.20	$250.20
Purchase #5	$12.44	12.848%	$14.0383	$14.04	$14.05	$14.00
Purchase #6	$146.44	5.592%	$154.6289	$154.63	$154.65	$154.60
Purchase #7	$198.69	12.629%	$223.7826	$223.78	$223.80	$223.80
7 purchase totals =	$934.27		$1,002.5262	$1,002.52	$1,002.55	$1,002.50