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	$117.95	11.802%	$131.8705	$131.87	$131.85	$131.90
Purchase #2	$180.49	11.275%	$200.8402	$200.84	$200.85	$200.80
Purchase #3	$156.60	5.288%	$164.881	$164.88	$164.90	$164.90
Purchase #4	$97.35	12.515%	$109.5334	$109.53	$109.55	$109.50
Purchase #5	$160.51	9.616%	$175.9446	$175.94	$175.95	$175.90
Purchase #6	$189.26	12.359%	$212.6506	$212.65	$212.65	$212.70
Purchase #7	$33.48	7.454%	$35.9756	$35.98	$36.00	$36.00
7 purchase totals =	$935.64		$1,031.6959	$1,031.69	$1,031.75	$1,031.70