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	$148.42	12.834%	$167.4682	$167.47	$167.45	$167.50
Purchase #2	$176.65	8.650%	$191.9302	$191.93	$191.95	$191.90
Purchase #3	$171.77	4.267%	$179.0994	$179.10	$179.10	$179.10
Purchase #4	$142.79	3.240%	$147.4164	$147.42	$147.40	$147.40
Purchase #5	$240.87	10.570%	$266.33	$266.33	$266.35	$266.30
Purchase #6	$94.39	9.609%	$103.4599	$103.46	$103.45	$103.50
Purchase #7	$37.88	6.850%	$40.4748	$40.47	$40.45	$40.50
7 purchase totals =	$1,012.77		$1,096.1789	$1,096.18	$1,096.15	$1,096.20