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	$123.53	3.477%	$127.8251	$127.83	$127.85	$127.80
Purchase #2	$175.65	5.546%	$185.3915	$185.39	$185.40	$185.40
Purchase #3	$27.41	6.504%	$29.1927	$29.19	$29.20	$29.20
Purchase #4	$163.42	4.851%	$171.3475	$171.35	$171.35	$171.30
Purchase #5	$192.47	3.459%	$199.1275	$199.13	$199.15	$199.10
Purchase #6	$29.41	8.225%	$31.829	$31.83	$31.85	$31.80
Purchase #7	$7.88	3.276%	$8.1381	$8.14	$8.15	$8.10
7 purchase totals =	$719.77		$752.8514	$752.86	$752.95	$752.70