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	$118.95	10.484%	$131.4207	$131.42	$131.40	$131.40
Purchase #2	$139.74	5.440%	$147.3419	$147.34	$147.35	$147.30
Purchase #3	$17.54	4.839%	$18.3888	$18.39	$18.40	$18.40
Purchase #4	$163.82	13.506%	$185.9455	$185.95	$185.95	$185.90
Purchase #5	$16.63	10.434%	$18.3652	$18.37	$18.35	$18.40
Purchase #6	$38.83	5.532%	$40.9781	$40.98	$41.00	$41.00
Purchase #7	$137.97	9.843%	$151.5504	$151.55	$151.55	$151.60
7 purchase totals =	$633.48		$693.9906	$694.00	$694.00	$694.00