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	$68.84	7.469%	$73.9817	$73.98	$74.00	$74.00
Purchase #2	$74.65	4.412%	$77.9436	$77.94	$77.95	$77.90
Purchase #3	$243.57	4.653%	$254.9033	$254.90	$254.90	$254.90
Purchase #4	$10.58	3.247%	$10.9235	$10.92	$10.90	$10.90
Purchase #5	$75.81	3.345%	$78.3458	$78.35	$78.35	$78.30
Purchase #6	$135.35	5.545%	$142.8552	$142.86	$142.85	$142.90
Purchase #7	$175.45	6.270%	$186.4507	$186.45	$186.45	$186.50
7 purchase totals =	$784.25		$825.4038	$825.40	$825.40	$825.40