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	$170.88	4.490%	$178.5525	$178.55	$178.55	$178.60
Purchase #2	$195.86	13.724%	$222.7398	$222.74	$222.75	$222.70
Purchase #3	$247.86	3.295%	$256.027	$256.03	$256.05	$256.00
Purchase #4	$152.91	12.308%	$171.7302	$171.73	$171.75	$171.70
Purchase #5	$131.30	8.727%	$142.7586	$142.76	$142.75	$142.80
Purchase #6	$146.59	6.322%	$155.8574	$155.86	$155.85	$155.90
Purchase #7	$177.84	10.524%	$196.5559	$196.56	$196.55	$196.60
7 purchase totals =	$1,223.24		$1,324.2214	$1,324.23	$1,324.25	$1,324.30