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	$126.37	11.106%	$140.4047	$140.40	$140.40	$140.40
Purchase #2	$218.59	13.304%	$247.6712	$247.67	$247.65	$247.70
Purchase #3	$73.69	11.254%	$81.9831	$81.98	$82.00	$82.00
Purchase #4	$182.72	9.774%	$200.5791	$200.58	$200.60	$200.60
Purchase #5	$172.34	10.420%	$190.2978	$190.30	$190.30	$190.30
Purchase #6	$78.98	11.787%	$88.2894	$88.29	$88.30	$88.30
Purchase #7	$82.41	11.382%	$91.7899	$91.79	$91.80	$91.80
7 purchase totals =	$935.10		$1,041.0152	$1,041.01	$1,041.05	$1,041.10