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	$147.44	11.175%	$163.9164	$163.92	$163.90	$163.90
Purchase #2	$57.65	6.372%	$61.3235	$61.32	$61.30	$61.30
Purchase #3	$91.54	6.578%	$97.5615	$97.56	$97.55	$97.60
Purchase #4	$247.25	12.452%	$278.0376	$278.04	$278.05	$278.00
Purchase #5	$33.59	3.746%	$34.8483	$34.85	$34.85	$34.80
Purchase #6	$180.35	11.416%	$200.9388	$200.94	$200.95	$200.90
Purchase #7	$160.74	3.276%	$166.0058	$166.01	$166.00	$166.00
7 purchase totals =	$918.56		$1,002.6319	$1,002.64	$1,002.60	$1,002.50