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	$116.85	9.472%	$127.918	$127.92	$127.90	$127.90
Purchase #2	$238.28	12.191%	$267.3287	$267.33	$267.35	$267.30
Purchase #3	$207.98	10.456%	$229.7264	$229.73	$229.75	$229.70
Purchase #4	$133.55	3.150%	$137.7568	$137.76	$137.75	$137.80
Purchase #5	$40.61	10.596%	$44.913	$44.91	$44.90	$44.90
Purchase #6	$77.73	6.590%	$82.8524	$82.85	$82.85	$82.90
Purchase #7	$136.55	12.208%	$153.22	$153.22	$153.20	$153.20
7 purchase totals =	$951.55		$1,043.7153	$1,043.72	$1,043.70	$1,043.70