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	$65.60	3.271%	$67.7458	$67.75	$67.75	$67.70
Purchase #2	$241.82	11.463%	$269.5398	$269.54	$269.55	$269.50
Purchase #3	$114.54	11.648%	$127.8816	$127.88	$127.90	$127.90
Purchase #4	$247.57	11.706%	$276.5505	$276.55	$276.55	$276.60
Purchase #5	$169.91	5.795%	$179.7563	$179.76	$179.75	$179.80
Purchase #6	$54.49	12.546%	$61.3263	$61.33	$61.35	$61.30
Purchase #7	$182.56	4.202%	$190.2312	$190.23	$190.25	$190.20
7 purchase totals =	$1,076.49		$1,173.0315	$1,173.04	$1,173.10	$1,173.00