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	$76.63	7.719%	$82.5451	$82.55	$82.55	$82.50
Purchase #2	$156.40	5.623%	$165.1944	$165.19	$165.20	$165.20
Purchase #3	$167.61	7.446%	$180.0902	$180.09	$180.10	$180.10
Purchase #4	$189.82	11.409%	$211.4766	$211.48	$211.50	$211.50
Purchase #5	$49.43	3.297%	$51.0597	$51.06	$51.05	$51.10
Purchase #6	$156.91	6.105%	$166.4894	$166.49	$166.50	$166.50
Purchase #7	$17.76	4.748%	$18.6032	$18.60	$18.60	$18.60
7 purchase totals =	$814.56		$875.4586	$875.46	$875.50	$875.50