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	$53.95	5.352%	$56.8374	$56.84	$56.85	$56.80
Purchase #2	$31.38	13.411%	$35.5884	$35.59	$35.60	$35.60
Purchase #3	$126.53	10.247%	$139.4955	$139.50	$139.50	$139.50
Purchase #4	$94.73	9.161%	$103.4082	$103.41	$103.40	$103.40
Purchase #5	$33.80	13.362%	$38.3164	$38.32	$38.30	$38.30
Purchase #6	$218.57	12.363%	$245.5918	$245.59	$245.60	$245.60
Purchase #7	$187.59	5.765%	$198.4046	$198.40	$198.40	$198.40
7 purchase totals =	$746.55		$817.6423	$817.65	$817.65	$817.60