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	$250.63	5.209%	$263.6853	$263.69	$263.70	$263.70
Purchase #2	$155.73	12.414%	$175.0623	$175.06	$175.05	$175.10
Purchase #3	$146.65	7.864%	$158.1826	$158.18	$158.20	$158.20
Purchase #4	$31.60	3.507%	$32.7082	$32.71	$32.70	$32.70
Purchase #5	$43.81	11.467%	$48.8337	$48.83	$48.85	$48.80
Purchase #6	$153.95	6.821%	$164.4509	$164.45	$164.45	$164.50
Purchase #7	$144.73	12.336%	$162.5839	$162.58	$162.60	$162.60
7 purchase totals =	$927.10		$1,005.5069	$1,005.50	$1,005.55	$1,005.60