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	$50.81	9.801%	$55.7899	$55.79	$55.80	$55.80
Purchase #2	$191.96	6.331%	$204.113	$204.11	$204.10	$204.10
Purchase #3	$141.83	4.306%	$147.9372	$147.94	$147.95	$147.90
Purchase #4	$182.44	7.225%	$195.6213	$195.62	$195.60	$195.60
Purchase #5	$215.50	6.407%	$229.3071	$229.31	$229.30	$229.30
Purchase #6	$155.80	10.676%	$172.4332	$172.43	$172.45	$172.40
Purchase #7	$32.86	13.735%	$37.3733	$37.37	$37.35	$37.40
7 purchase totals =	$971.20		$1,042.5750	$1,042.57	$1,042.55	$1,042.50