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	$205.99	11.323%	$229.3142	$229.31	$229.30	$229.30
Purchase #2	$202.86	13.177%	$229.5909	$229.59	$229.60	$229.60
Purchase #3	$25.87	9.751%	$28.3926	$28.39	$28.40	$28.40
Purchase #4	$59.38	4.589%	$62.1049	$62.10	$62.10	$62.10
Purchase #5	$203.58	6.503%	$216.8188	$216.82	$216.80	$216.80
Purchase #6	$103.55	10.538%	$114.4621	$114.46	$114.45	$114.50
Purchase #7	$142.94	13.711%	$162.5385	$162.54	$162.55	$162.50
7 purchase totals =	$944.17		$1,043.2220	$1,043.21	$1,043.20	$1,043.20