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	$59.75	13.345%	$67.7236	$67.72	$67.70	$67.70
Purchase #2	$94.65	6.540%	$100.8401	$100.84	$100.85	$100.80
Purchase #3	$241.61	12.534%	$271.8934	$271.89	$271.90	$271.90
Purchase #4	$237.32	9.158%	$259.0538	$259.05	$259.05	$259.10
Purchase #5	$201.98	5.837%	$213.7696	$213.77	$213.75	$213.80
Purchase #6	$110.30	13.858%	$125.5854	$125.59	$125.60	$125.60
Purchase #7	$46.53	12.441%	$52.3188	$52.32	$52.30	$52.30
7 purchase totals =	$992.14		$1,091.1847	$1,091.18	$1,091.15	$1,091.20