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	$163.89	9.666%	$179.7316	$179.73	$179.75	$179.70
Purchase #2	$203.52	6.827%	$217.4143	$217.41	$217.40	$217.40
Purchase #3	$40.84	6.588%	$43.5305	$43.53	$43.55	$43.50
Purchase #4	$61.73	3.741%	$64.0393	$64.04	$64.05	$64.00
Purchase #5	$190.34	3.390%	$196.7925	$196.79	$196.80	$196.80
Purchase #6	$174.94	13.453%	$198.4747	$198.47	$198.45	$198.50
Purchase #7	$186.39	6.211%	$197.9667	$197.97	$197.95	$198.00
7 purchase totals =	$1,021.65		$1,097.9496	$1,097.94	$1,097.95	$1,097.90