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	$58.78	5.499%	$62.0123	$62.01	$62.00	$62.00
Purchase #2	$8.59	3.829%	$8.9189	$8.92	$8.90	$8.90
Purchase #3	$159.34	4.527%	$166.5533	$166.55	$166.55	$166.60
Purchase #4	$141.36	6.505%	$150.5555	$150.56	$150.55	$150.60
Purchase #5	$62.47	7.790%	$67.3364	$67.34	$67.35	$67.30
Purchase #6	$78.99	8.736%	$85.8906	$85.89	$85.90	$85.90
Purchase #7	$47.75	6.180%	$50.701	$50.70	$50.70	$50.70
7 purchase totals =	$557.28		$591.9680	$591.97	$591.95	$592.00