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	$246.33	8.727%	$267.8272	$267.83	$267.85	$267.80
Purchase #2	$234.66	3.390%	$242.615	$242.62	$242.60	$242.60
Purchase #3	$154.73	3.667%	$160.4039	$160.40	$160.40	$160.40
Purchase #4	$96.68	7.459%	$103.8914	$103.89	$103.90	$103.90
Purchase #5	$199.85	11.134%	$222.1013	$222.10	$222.10	$222.10
Purchase #6	$131.92	8.137%	$142.6543	$142.65	$142.65	$142.70
Purchase #7	$103.83	7.612%	$111.7335	$111.73	$111.75	$111.70
7 purchase totals =	$1,168.00		$1,251.2266	$1,251.22	$1,251.25	$1,251.20