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	$202.45	6.841%	$216.2996	$216.30	$216.30	$216.30
Purchase #2	$31.60	7.159%	$33.8622	$33.86	$33.85	$33.90
Purchase #3	$110.84	11.461%	$123.5434	$123.54	$123.55	$123.50
Purchase #4	$173.29	10.404%	$191.3191	$191.32	$191.30	$191.30
Purchase #5	$102.60	13.486%	$116.4366	$116.44	$116.45	$116.40
Purchase #6	$109.63	4.500%	$114.5634	$114.56	$114.55	$114.60
Purchase #7	$235.69	11.178%	$262.0354	$262.04	$262.05	$262.00
7 purchase totals =	$966.10		$1,058.0597	$1,058.06	$1,058.05	$1,058.00