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	$176.46	4.589%	$184.5577	$184.56	$184.55	$184.60
Purchase #2	$52.70	12.318%	$59.1916	$59.19	$59.20	$59.20
Purchase #3	$63.97	5.469%	$67.4685	$67.47	$67.45	$67.50
Purchase #4	$240.56	4.290%	$250.88	$250.88	$250.90	$250.90
Purchase #5	$198.94	12.273%	$223.3559	$223.36	$223.35	$223.40
Purchase #6	$153.80	9.247%	$168.0219	$168.02	$168.00	$168.00
Purchase #7	$187.60	11.359%	$208.9095	$208.91	$208.90	$208.90
7 purchase totals =	$1,074.03		$1,162.3851	$1,162.39	$1,162.35	$1,162.50