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	$115.78	13.447%	$131.3489	$131.35	$131.35	$131.30
Purchase #2	$199.87	11.120%	$222.0955	$222.10	$222.10	$222.10
Purchase #3	$161.47	11.787%	$180.5025	$180.50	$180.50	$180.50
Purchase #4	$86.49	7.297%	$92.8012	$92.80	$92.80	$92.80
Purchase #5	$217.41	11.866%	$243.2079	$243.21	$243.20	$243.20
Purchase #6	$234.92	8.334%	$254.4982	$254.50	$254.50	$254.50
Purchase #7	$141.52	4.119%	$147.3492	$147.35	$147.35	$147.30
7 purchase totals =	$1,157.46		$1,271.8034	$1,271.81	$1,271.80	$1,271.70