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	$107.69	3.643%	$111.6131	$111.61	$111.60	$111.60
Purchase #2	$117.98	10.241%	$130.0623	$130.06	$130.05	$130.10
Purchase #3	$149.79	12.797%	$168.9586	$168.96	$168.95	$169.00
Purchase #4	$38.87	9.644%	$42.6186	$42.62	$42.60	$42.60
Purchase #5	$134.30	11.260%	$149.4222	$149.42	$149.40	$149.40
Purchase #6	$69.43	3.832%	$72.0906	$72.09	$72.10	$72.10
Purchase #7	$182.55	6.604%	$194.6056	$194.61	$194.60	$194.60
7 purchase totals =	$800.61		$869.3710	$869.37	$869.30	$869.40