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	$57.40	7.591%	$61.7572	$61.76	$61.75	$61.80
Purchase #2	$167.65	11.853%	$187.5216	$187.52	$187.50	$187.50
Purchase #3	$68.67	5.565%	$72.4915	$72.49	$72.50	$72.50
Purchase #4	$150.91	4.731%	$158.0496	$158.05	$158.05	$158.00
Purchase #5	$99.51	6.248%	$105.7274	$105.73	$105.75	$105.70
Purchase #6	$243.80	6.135%	$258.7571	$258.76	$258.75	$258.80
Purchase #7	$77.56	9.511%	$84.9367	$84.94	$84.95	$84.90
7 purchase totals =	$865.50		$929.2411	$929.25	$929.25	$929.20