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	$151.73	7.295%	$162.7987	$162.80	$162.80	$162.80
Purchase #2	$124.36	13.377%	$140.9956	$141.00	$141.00	$141.00
Purchase #3	$11.78	13.153%	$13.3294	$13.33	$13.35	$13.30
Purchase #4	$19.25	7.440%	$20.6822	$20.68	$20.70	$20.70
Purchase #5	$244.56	11.225%	$272.0119	$272.01	$272.00	$272.00
Purchase #6	$133.27	7.179%	$142.8375	$142.84	$142.85	$142.80
Purchase #7	$164.32	9.281%	$179.5705	$179.57	$179.55	$179.60
7 purchase totals =	$849.27		$932.2258	$932.23	$932.25	$932.20