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	$176.92	4.827%	$185.4599	$185.46	$185.45	$185.50
Purchase #2	$75.47	3.712%	$78.2714	$78.27	$78.25	$78.30
Purchase #3	$60.60	7.428%	$65.1014	$65.10	$65.10	$65.10
Purchase #4	$222.42	10.648%	$246.1033	$246.10	$246.10	$246.10
Purchase #5	$91.98	12.820%	$103.7718	$103.77	$103.75	$103.80
Purchase #6	$136.95	3.800%	$142.1541	$142.15	$142.15	$142.20
Purchase #7	$137.32	12.348%	$154.2763	$154.28	$154.30	$154.30
7 purchase totals =	$901.66		$975.1382	$975.13	$975.10	$975.30