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	$92.50	13.135%	$104.6499	$104.65	$104.65	$104.60
Purchase #2	$65.84	6.280%	$69.9748	$69.97	$69.95	$70.00
Purchase #3	$59.76	13.114%	$67.5969	$67.60	$67.60	$67.60
Purchase #4	$225.61	3.328%	$233.1183	$233.12	$233.10	$233.10
Purchase #5	$100.32	6.442%	$106.7826	$106.78	$106.80	$106.80
Purchase #6	$166.82	12.433%	$187.5607	$187.56	$187.55	$187.60
Purchase #7	$90.85	5.448%	$95.7995	$95.80	$95.80	$95.80
7 purchase totals =	$801.70		$865.4827	$865.48	$865.45	$865.50