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	$249.57	8.759%	$271.4298	$271.43	$271.45	$271.40
Purchase #2	$143.44	10.381%	$158.3305	$158.33	$158.35	$158.30
Purchase #3	$216.82	3.254%	$223.8753	$223.88	$223.90	$223.90
Purchase #4	$12.96	8.777%	$14.0975	$14.10	$14.10	$14.10
Purchase #5	$244.38	4.459%	$255.2769	$255.28	$255.30	$255.30
Purchase #6	$45.89	10.415%	$50.6694	$50.67	$50.65	$50.70
Purchase #7	$207.86	5.126%	$218.5149	$218.51	$218.50	$218.50
7 purchase totals =	$1,120.92		$1,192.1943	$1,192.20	$1,192.25	$1,192.20