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	$177.64	4.636%	$185.8754	$185.88	$185.90	$185.90
Purchase #2	$139.47	10.193%	$153.6862	$153.69	$153.70	$153.70
Purchase #3	$38.77	6.298%	$41.2117	$41.21	$41.20	$41.20
Purchase #4	$123.60	3.311%	$127.6924	$127.69	$127.70	$127.70
Purchase #5	$246.55	7.329%	$264.6196	$264.62	$264.60	$264.60
Purchase #6	$155.73	7.771%	$167.8318	$167.83	$167.85	$167.80
Purchase #7	$144.97	5.358%	$152.7375	$152.74	$152.75	$152.70
7 purchase totals =	$1,026.73		$1,093.6546	$1,093.66	$1,093.70	$1,093.60