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	$116.52	9.285%	$127.3389	$127.34	$127.35	$127.30
Purchase #2	$40.54	3.162%	$41.8219	$41.82	$41.80	$41.80
Purchase #3	$19.99	10.649%	$22.1187	$22.12	$22.10	$22.10
Purchase #4	$56.28	6.453%	$59.9117	$59.91	$59.90	$59.90
Purchase #5	$46.54	9.270%	$50.8543	$50.85	$50.85	$50.90
Purchase #6	$226.94	6.275%	$241.1805	$241.18	$241.20	$241.20
Purchase #7	$137.39	3.596%	$142.3305	$142.33	$142.35	$142.30
7 purchase totals =	$644.20		$685.5565	$685.55	$685.55	$685.50