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	$246.40	12.175%	$276.3992	$276.40	$276.40	$276.40
Purchase #2	$41.49	11.475%	$46.251	$46.25	$46.25	$46.30
Purchase #3	$174.37	11.159%	$193.8279	$193.83	$193.85	$193.80
Purchase #4	$146.78	6.747%	$156.6832	$156.68	$156.70	$156.70
Purchase #5	$110.57	5.296%	$116.4258	$116.43	$116.45	$116.40
Purchase #6	$178.70	6.498%	$190.3119	$190.31	$190.30	$190.30
Purchase #7	$188.41	4.467%	$196.8263	$196.83	$196.85	$196.80
7 purchase totals =	$1,086.72		$1,176.7253	$1,176.73	$1,176.80	$1,176.70