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	$135.51	13.615%	$153.9597	$153.96	$153.95	$154.00
Purchase #2	$178.94	9.717%	$196.3276	$196.33	$196.35	$196.30
Purchase #3	$99.46	4.474%	$103.9098	$103.91	$103.90	$103.90
Purchase #4	$88.37	12.237%	$99.1838	$99.18	$99.20	$99.20
Purchase #5	$152.33	13.248%	$172.5107	$172.51	$172.50	$172.50
Purchase #6	$142.95	9.696%	$156.8104	$156.81	$156.80	$156.80
Purchase #7	$148.45	8.292%	$160.7595	$160.76	$160.75	$160.80
7 purchase totals =	$946.01		$1,043.4615	$1,043.46	$1,043.45	$1,043.50