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	$167.94	13.608%	$190.7933	$190.79	$190.80	$190.80
Purchase #2	$241.65	13.678%	$274.7029	$274.70	$274.70	$274.70
Purchase #3	$59.47	10.814%	$65.9011	$65.90	$65.90	$65.90
Purchase #4	$161.56	9.723%	$177.2685	$177.27	$177.25	$177.30
Purchase #5	$122.76	3.797%	$127.4212	$127.42	$127.40	$127.40
Purchase #6	$187.29	12.599%	$210.8867	$210.89	$210.90	$210.90
Purchase #7	$119.59	6.769%	$127.685	$127.69	$127.70	$127.70
7 purchase totals =	$1,060.26		$1,174.6587	$1,174.66	$1,174.65	$1,174.70