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	$136.91	10.813%	$151.7141	$151.71	$151.70	$151.70
Purchase #2	$244.36	3.768%	$253.5675	$253.57	$253.55	$253.60
Purchase #3	$160.57	9.807%	$176.3171	$176.32	$176.30	$176.30
Purchase #4	$173.50	12.106%	$194.5039	$194.50	$194.50	$194.50
Purchase #5	$136.63	5.317%	$143.8946	$143.89	$143.90	$143.90
Purchase #6	$37.54	8.713%	$40.8109	$40.81	$40.80	$40.80
Purchase #7	$83.39	3.737%	$86.5063	$86.51	$86.50	$86.50
7 purchase totals =	$972.90		$1,047.3144	$1,047.31	$1,047.25	$1,047.30