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	$56.64	13.758%	$64.4325	$64.43	$64.45	$64.40
Purchase #2	$79.69	7.775%	$85.8859	$85.89	$85.90	$85.90
Purchase #3	$51.70	4.735%	$54.148	$54.15	$54.15	$54.10
Purchase #4	$160.92	6.738%	$171.7628	$171.76	$171.75	$171.80
Purchase #5	$24.96	3.266%	$25.7752	$25.78	$25.80	$25.80
Purchase #6	$118.35	5.480%	$124.8356	$124.84	$124.85	$124.80
Purchase #7	$174.25	10.474%	$192.5009	$192.50	$192.50	$192.50
7 purchase totals =	$666.51		$719.3409	$719.35	$719.40	$719.30