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	$244.78	9.400%	$267.7893	$267.79	$267.80	$267.80
Purchase #2	$105.82	5.632%	$111.7798	$111.78	$111.80	$111.80
Purchase #3	$89.94	9.648%	$98.6174	$98.62	$98.60	$98.60
Purchase #4	$136.39	4.504%	$142.533	$142.53	$142.55	$142.50
Purchase #5	$172.33	12.434%	$193.7575	$193.76	$193.75	$193.80
Purchase #6	$176.37	7.588%	$189.753	$189.75	$189.75	$189.80
Purchase #7	$109.30	3.367%	$112.9801	$112.98	$113.00	$113.00
7 purchase totals =	$1,034.93		$1,117.2101	$1,117.21	$1,117.25	$1,117.30