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	$174.85	4.145%	$182.0975	$182.10	$182.10	$182.10
Purchase #2	$145.33	13.795%	$165.3783	$165.38	$165.40	$165.40
Purchase #3	$38.72	12.171%	$43.4326	$43.43	$43.45	$43.40
Purchase #4	$28.64	3.392%	$29.6115	$29.61	$29.60	$29.60
Purchase #5	$177.66	3.290%	$183.505	$183.51	$183.50	$183.50
Purchase #6	$231.81	8.148%	$250.6979	$250.70	$250.70	$250.70
Purchase #7	$196.87	6.835%	$210.3261	$210.33	$210.35	$210.30
7 purchase totals =	$993.88		$1,065.0489	$1,065.06	$1,065.10	$1,065.00